- "Sink your teeth into victory! Join Mental's Horde!"
- ―Mental's Horde propaganda poster[src]
Mental's Horde is the name given to the forces encountered in the Serious Sam series and are controlled by Mental, Serious Sam's arch nemesis. They are incalculable in number and very dangerous, capable of overrunning every planet they attack. However, they generally lack tactics and often just charge into enemy lines of fire, meaning they lose enormous casualties in the process. This does not appear to obstruct them however.
Mental (also known as Tah-Um or Chaad Sheen) is the primary antagonist in the Serious Sam series. Mental is the last of of the Hum-Ta, a species of god-like rulers that ruled over galaxies peacefully.
However, something happened to Mental, and instead he decided to wipe out the empire and make it his goal to kill intelligent life every couple hundred thousand of years or so. In between the years, he would sleep and deactivate his forces. However, when he detected them, he wakes up and activates his forces. Mental utilizes both technology and magic in order to achieve his goals. The diversity can be seen in his army, where he uses cyborgs, executed enemy soldiers raised from the dead, reanimated skeletons of long extinct races, clones, creatures made out of pure magic, robots, mercenaries, or even plain vehicles.
These creatures seem to be made in very large numbers, which is possibly why Mental always manages to defeat any species he encounters. He also recruits primitive races in order to bolster his ranks. He has created agreements with creatures such as the Aludran Reptiloids in order for them to work for him and has even tampered with the evolutionary paths of some creatures so he can mold them into troops for his purpose. He uses several methods to coerce races into working with him. In the case of the Aludran Reptiliods, he offered them magical combat abilities. In other cases, such as the Zorg, he simply paid for massive amounts of disposable troops. This isn't to say that Mental has no intelligent creatures working with and for him, however. Ugh-Zan III and Ugh-Zan IV appear to be intelligent enough to be things such as admirals in Mental's army, and Mordekai the Summoner was intelligent enough to properly use and research magic.
This are most likely exceptions. Mental's appearance is unknown. Based on his logos, it's possible he's a creature like Chluthu with tentacles on his face, as his logos seem to have tentacles that are on a face. Mental is the last of the Hum-Ta, extremely powerful rulers of large, intergalactic empires. His predecessors had peacefully and wisely ruled the empires, but Mental was different. For some reason, he became dedicated to wiping out all intelligent life. He destroyed the empires, then disappeared for thousands of years. He returned to kill any intelligent life that had appeared with an army made out of robots, magical powers, and genetically engineered species, such as the Biomechanoid. Later, a species called the Ellians had discovered the remains of the old empires once ruled by the Hum-Ta and pieced together who Mental was. Before they could do anything, Mental returned and destroyed them, then disappeared soon afterwards.
Many, many years after the fall of the Ellians, the Sirians appeared and helped more primitive species, such as the Kleers. During their travels, the Sirians discovered ruins from when the Ellians existed. It informed them of what Mental was. However, like the Ellians, Mental returned soon after the Sirians read about him in the Ellians' ruins. Mental began waging war against them, resurrecting and recruiting their fallen soldiers as members of his army. Soon enough, it had wiped out all of Sirius and its colonies, including firebombing the Kleers and reanimating their skeletons. Unknown to Mental was that Sirians had one more of its search parties out in the universe, which resided on Earth. Theses Sirians had left much of their technology and warnings about Mental to the Earthlings.
After wiping out the Sirians, Mental left as he usually did, but was suspicious and felt that there might've been more intelligent life out there. He set up a large asteroid belt around what was Sirius in order to serve as an alarm in case his suspicions were correct and nosy intelligent life was flying around in space. Around two thousand years later, humans discover old Sirian technology buried under old Ancient Egyptian ruins. After some reverse-engineering, humans obtained ways to travel to the stars with ease. An exploratory force lead by Serious Sam is sent to chart out the remains of Sirius for a corporation. However, there is something unusual; the planet is surrounded by an asteroid belt not mentioned in the records. Sam, pressured by the corporations, goes through the asteroid belt and explores it.
This triggers the alarm system, which wakes up Mental much earlier than planned. By the time Serious Sam 3: BFE has started, it is clear that humanity has lost. All humans in Cairo have been wiped out by Mental, and it seems that all that is left is a small group of Earth Defense Force soldiers posted somewhat near Cairo. The humans have placed their last hope on the Time-Lock, which is something that Mental seems to be unaware of. During Serious Sam's journey to power up the Time-Lock, Mental stages a final attack on the Earth Defense Force's HQ, completely wiping it out. Now that the last bit of resistance has been wiped out, Mental starts preparing to drop the Moon towards Earth in order to blow Earth up. Sam, however, is fighting towards the Time-Lock, hoping to get in there to give humans one last chance.
Mental attempts to stall Sam long enough so that he can be crushed by the Moon by sending in huge amounts of monsters and even Ugh-Zan IV, one of his trusted subordinates, but Sam manages to defeat them, including the dreaded warlock. As Sam is walking towards the Time-Lock, he decides to call Mental and threaten him, but instead, he gets Mental's daughter. After a brief chit-chat, she tells Sam about her dad blowing up Earth with the Moon. Right afterwards, Sam sees the Moon hurtling towards the Earth, so he quickly runs into the Time-Lock right before the Moon hits and blows up Earth. In this timeline, Mental managed to finish off humanity, just like all the other species that encountered him. After Sam uses the Time-Lock, he warps back to Ancient Egypt. As expected, the Time-Lock alerts Mental from that time period that there is intelligent life on Earth, so he sends some of his forces to slaughter humans back then. This Mental is unaware of Sam's abilities at first, and sends only weak forces at him. However, after Sam slaughters them, he begins sending in more and stronger forces, such as the Highlander Aludran Reptiloid, against him. Sam still manages to slaughter every creature that Mental sends at him.
Knowing that something major is up, he sends Ugh-Zan III at Sam while he is approaching the Great Pyramid. Sam manages to retreat to the Great Pyramid and reach its top while the ship is parked. Ugh-Zan III scales the pyramid in order to finish off Sam, but Sam manages to manipulate the ship's security system to kill Ugh-Zan III. After Ugh-Zan III is dead, Sam boards the ship and calls up Mental, who is not at home at the moment. By the time Sam crash-lands on Earth again, Mental is well aware of Sam's abilities and tries to stop him with stronger and newer forces from the start. He seems to be somewhat aware of Sam's plan to get a backup ship, as he does things such as install the Exotech Larva in front of the portal to medieval Europe. He even manages to steal the Holy Grail, which is used to activate the backup Sirian ship Sam is looking for, but is unable to use or destroy it because he nor his creatures are authorized to use it because of how evil they are. Sam manages to defeat the Holy Grail's guardian, Mordekai the Summoner, and uses it to activate the ship. Before he leaves, he calls up Mental and mocks him by pretending to apologize for killing his monsters and troops.
When Sam is warped to the last of the Sirian's home, he is informed that Mental has one large weakness: a medallion. However, the parts have been scattered throughout the galaxy in order to prevent anyone from using it against him. Armed with this knowledge, Sam sets out to get each of the pieces and remake the Medallion. After clearing out Mental's forces from several planets, he finally makes the Medallion and intends to use it on Mental. Sam managed to pierce the defense shield on Sirius just long enough to enter Sirius, where he did battle against Mental's forces on his home turf. After many battles on Sirius, Sam managed to find Mental's base, the Mental Institution. After fighting off many enemies, including the base itself, Sam finally managed to get to Mental and finish him off once and for all. However, little did Sam know that Mental was already preparing to leave and sent a decoy voicebox in a dark room to distract Sam long enough so that he can escape. By the time Sam discovered the decoy, Mental was already leaving Sirius and heading out to another part of space. Sometime later, Sam returned to the Sirian's home and informed them about what happened. While talking to them, he noticed a large box of medallions in the room. Sam learned that the Medallion was actually worthless and that there were plenty of them.
- Ugh-Zan III is the final boss in Serious Sam: The First Encounter and Serious Sam HD: The First Encounter. Ugh-Zan III is one of Mental's generals, ranking as Great Admiral in Mental's Horde. Ugh-Zan III is the third incarnation of the vicious Ugh-Zan, the last of the warlock giants. He was sent by Mental to supervise the assault on Earth. He is one of the most dangerous creatures in the universe. Ugh-Zan III is a very large creature, but very slow. He moves at the same speed as the player does (10 speed in the database, just like Sam), has 4 arms, which comes with 4 weapons, can breath fireballs or stomp the player and can regenerate his health when it's low. He regenerates his life when he has about to 5% health left (when the life bar turns red and is nearly empty). He is stunned, disabled and immobilized when hit by the laser beam, so he can't regenerate. The boss fight comes in 3 stages; running away from him, waiting for the Pyramid Door to open and the last fight. In the first stage, you just run away from him, as he chases you through the Arena to the Great Pyramid. While you're doing this, Biomechanoid Minors, Biomechanoid Majors, Kleer Skeletons, and Sirian Werebulls are rushing you. In the second stage, you will have to survive against him until the Pyramid Door opens, which will take some time. Ugh-Zan will take out his Lava Bomb Launcher and Laser Gun when he reaches the Pyramid's ramp. In the third stage, he will jump inside the Pyramid Arena, pull out all his 4 weapons (Lava Bomb Launcher, Rocket Launcher, Laser Gun and Electric Gun). To kill him, you will have to activate all four rings around the arena, get him in the middle and zap him with the spaceship's laser beam. In SSHD, a laser beam is automatically fired once when you enter the pyramid.
- Ugh-Zan IV is the final boss in Serious Sam 3: BFE and the biological father of Ugh-Zan III, due to some paradox caused by a time traveling accident. Ugh-Zan IV is a very large creature, which moves quite fast due to his vast size and will stomp the player at every opportunity. He's generally not considered as difficult as Ugh-Zan III. He has very high health regeneration that increases the lower he is on health, and while regenerating, cannot be killed with any of Sam's weapons. He'll stomp you if given the opportunity, and fires wide, fast-moving projectiles that, while easily dodged, do considerable damage. Ugh-Zan is constantly surrounded by Mental's forces and will spawn in reinforcements until either he or Sam is dead. He, along with his infinite horde of alien backup, is Mental's last defense against Sam and the Time-Lock - or so Sam thinks.
- The Beheaded Rocketeer appears as a headless, purple t-shirt-wearing man holding a gun and a head. The Rocketeer is made from an executed Sirian soldier raised from the dead with a "Life Control Unit". Rocketeers are equipped with a magic missile launcher on their right and and hold their head on the left, which is used to obtain visual and sound data. In Serious Sam HD, the Rocketeer has a saw on his neck, holds his gun with his left hand and his head with his right. The Rocketeer fires a magical missile that does minimal damage and takes time to get to its target, making them easy to dodge. They have very low health and can be easily killed with any weapon in the game. They are essentially cannon-fodder, even at high difficulty levels.
- The Beheaded Bomber appears as a headless, green t-shirt-wearing man. What it is holding depends on the game; in Serious Sam 1, he holds a head with his left hand. In Serious Sam HD, his head is impaled on a spike that is located on his neck and holds a bag of grenades with his right hand. The Bomber is made from an executed Sirian soldier raised from the dead with a "Life Control Unit". Bombers are equipped with inflatable bombs made from Sirian toys. The Bomber's only attack is throwing grenades. These grenades make little noise until they hit the ground or the player. Grenades have a small splash damage radius compared to the player's MK III Grenade Launcher grenades. When killed, the Bomber will explode. The Bomber's grenades can be shot in mid-air.
- The Beheaded Firecracker appears as a headless, red t-shirt-wearing man. What it is holding depends on the game: in Serious Sam 1, he holds a claw-like gun and a head. In Serious Sam HD, he holds a chainsaw and a head. The Firecracker is made from an executed Sirian soldier raised from the dead with a "Life Control Unit". Firecrackers are equipped with a magic missile launcher on their right and and hold their head on the left, which is used to obtain visual and sound data. Firecrackers fire a spread of magic missiles that will spread from the Firecracker, hit the ground and quickly follow the ground until they hit something. In Serious Sam HD, the Firecracker will use its chainsaw if the player gets too close to it.
- The Beheaded Kamikaze appears as a headless and shirtless man holding two bombs. The Kamikaze is made from an executed Sirian soldier raised from the dead with a "Life Control Unit". Kamikazes are equipped with a recorder that emits a very loud scream while the Kamikaze is charging towards its victim. In general, Kamikazes are one of the most dangerous enemy types in the game. They are very fast and can sneak up on the player and inflict a large amount of damage, especially in harder difficulties. Groups of Kamikazes exploding at once can be an instant-kill to a player in harder difficulties, even if they have a lot of health and armor. In addition, they explode when they die, making them dangerous if they manage to sneak up to the player, but don't manage to get close enough to explode on their own.
- Kleer Skeletons are undead creatures from planet Kleer. They were always skeletons, as seen in Serious Sam 2. They can summon Chain-Balls by clapping their hands together. They have sharp claws, fangs and horns. Their skeleton looks humanoid, except the legs, hands and head. A Kleer can either slash the player when too close, cast its Chain-Balls from range or jump on the player. They usually run, stop, cast their Chain-Balls and repeat the sequence. When too close to the player they jump, and if they hit him/her, they usually slash him. The player can't outrun a Kleer Skeleton when it's too close. Kleer Skeletons are one of the basic enemies in the Serious Sam series.
- The Sirian Werebull is a strange mixture of Sirian and cattle DNA. Unlike regular cattle, the Werebull has fingers. It is unknown if the Werebull was made by Mental or by the Sirians themselves. The Werebull has medium health and is very fast, making it a dangerous foe. Its two attacks consist of ramming the player, which causes the player to go flying into the air, or if the player is not fast enough, it will attempt to gore the player with its horns, causing more damage than a ram would.
- Biomechanoid Minors are bipedal cyborgs with robotic chicken legs and a small blue bodythat has two Laserguns attached to its sides. They have been designed by Mental from the ground-up from avian DNA, allowing him to customize them to his needs. They run on a battery that can be recharged by hooking it up to an external power source. Compared to their Major counterparts, Minors are smaller, have less health and does less damage. They are as fast as Majors though. The Minor's fire rate depends on the difficulty; in Tourist and Easy, it will fire slowly. In Normal and higher, it will fire at a fast rate. No matter the difficulty, the laser are fast-traveling and can quickly hit a non-moving target.
- Biomechanoid Majors are bipedal cyborgs with robotic chicken legs and a large red bodythat has two Rocket Launchers attached to its sides. They have been designed by Mental from the ground-up from avian DNA, allowing him to customize them to his needs. They run on a battery that can be recharged by hooking it up to an external power source. A Major does not fire its rockets simultaneously, which can help it target a particularly mobile target. For example, if the player is strafing right and a rocket misses, then starts strafing left, the second missile will fire at the player even though they are going in the opposite direction. After firing two missiles, the Major will have a brief cooldown period, then start firing again. Majors are one of the most deadly enemies in the game; they have high health and their rockets can inflict a lot of damage, especially if they explode close to the player.
- The Scythian Witch Harpy appears as a metal bikini-wearing woman with wings. She is a female clone of a long extinct Scythian race created by Mental. They are trained in casting magic spells and close quarters combat. Despite being able to use projectiles, the Harpy's AI makes her lean toward getting in close and using her melee attack. If a harpy is shot in the wings enough times, the Harpy will fall to the ground and continue attacking, then fly back up a few minutes later. Harpies have two attacks; throwing a slow magic ball and kicking.
- Common Aludran Reptiloids are usually found on heights, such as towers, so they can spot you easier. They only appear in The First Encounter, The Second Encounter, Serious Sam Xbox, and the two Serious Sam HD games. The Common ones are green four-handed creatures. Their appearance between the encounters and HD has changed a lot. Their heads are diifferent and the stomach as well. In Serious Sam HD they have unique animations. And now they don't have tattoos in their chest and feet, like the Highlanders. Also, they have no horns now.
- Highlander Aludran Reptiloids are usually mini-bosses in The First Encounter and big enemies in The Second Encounter. One was presented as a mini-boss. They only appear in The First Encounter, The Second Encounter, Serious Sam Xbox, and the two Serious Sam HD games. Their missiles are indestructible in Serious Sam HD. The Highlanders are big red four-handed creatures. Their appearance between the encounters and HD has changed a lot. Their head, first of all, has changed in all views. Their stomach looks different and now they have different animations apart from the common ones in Serious Sam HD. Their missiles have also changed. In The First Encounter they used their own ones and in Serious Sam Xbox and Serious Sam HD they used the common fireballs. Of course in HDthe fireballs are different, but they are still the common ones. And now they don't have tattoos in their chest and feet. And they don't have horns anymore.
- Arachnoids are essentially scorpions with human torsos where their head should be. The human part of the creature has a human hand for a right arm and a pincer on its left arm. They have a very violent culture in which struggles for dominance frequently take place. An Arachnoid's age can be measured by its exoskeleton color; young Arachnoids have a yellow exoskeleon, while adult Arachnoids have red exoskeletons. It appears that Mental has tampered with their genes, as Arachnoid legends state that a god came from the heavens and gave them a five-fingered right arm and told them to fight off any race it declares is an enemy. Arachnoids come in two variants; Juvenile and Adult. Juveniles have yellow skin, while Adults have red skin, are larger, have more health and do more damage compared to the Juvenile. Arachnoids have two attacks; burst-firing their minigun or stinging the player with their tail. The minigun has very good accuracy, making it a dangerous weapon at all ranges. The sting is only used if they player gets close to an Arachnoid, though most of the time its minigun will cut up the player long before the player can get in melee range.
- Marsh Hoppers are small, frog-like aliens originating from the planet Rigil Kentaurus. When it spots an enemy, they will hop towards the enemy until they get close enough to the enemy, where they will jump in on the enemy and explode, releasing toxic slime that is storied in their body. In-game, Hoppers have very low health, making them simple to kill. However, Hoppers are always released in large hordes. This makes them very dangerous, as they can quickly jump on the player in succession and inflict a lot of damage in a very short amount of time. In higher difficulties, a group of Hoppers jumping on the player almost at once can quickly kill a player with 80%+ health and no armor.
- A Reeban Electro-Fish is an aquatic animal from the planet Reeb. When it spots an enemy, it fires a bolt of electricity from the light attached to its head. The bolt will disorient the enemy upon contact, making it somewhat hard to hit the Electro-Fish for a second or two. This makes the Electro-Fish very dangerous in groups, as a constant barrage of lightning will constantly disorient the enemy, making it difficult for the victim to fight back without loosing a lot of health/armor, especially in higher difficulties.
- Lava Golems are piles of lava magically brought to life. While the first one that appears in the Serious Sam series is a guardian summoned by the collected elements, the rest of the Golems in the gamesappear to be made by Mental himself, as they spawn with Mental-allied enemies. There are three types of Lava Golem; small, medium and large. Each size has different health, damage dealt and point value. If a medium or large Golem is close to death, it will spawn small and medium Golems, respectively. The Lava Golem has two attacks; throwing chunks of lava or pounding the ground when the player gets close to it. When throwing lava balls, the AI will attempt to predict where the player is going and will try to throw a lava ball to what direction it perceives the player is going.
- Cucurbito the Pumpkin is a human wearing overalls, uses a chainsaw and has a pumpkin for a head. It was made by Mental by combining elements his time-traveling agents found in 20th-century Earth, including Smashing Pumpkins albums, a copy of the Burt Reynold's movie Deliverance and a copy of Lumberjack Digest. Cucurbitos only have one attack; charge at the player. The player can also be damaged by walking into a Cucurbito.
- The Zorg Mercenary is a bipedal, skinless lizard-like creature. its people, the Zorg, managed to create a large interstellar empire. After conquering enough planets, they decided to take a very long break by sunbathing from 10AM-4PM. The amount of sunbathing eventually caused their skin to fall off. Somehow, the Zorg began working with Mental after their disastrous vacation and now attempt to stop Serious Sam. The Mercenary's gun fires two lasers in quick succession. Generally, if one laser hits a target, the other will almost always as well because of how quickly they are fired.
- The Zorg Commander is a bipedal, skinless lizard-like creature. its people, the Zorg, managed to create a large interstellar empire. After conquering enough planets, they decided to take a very long break by sunbathing from 10AM-4PM. The amount of sunbathing eventually caused their skin to fall off. Somehow, the Zorg began working with Mental after their disastrous vacation and now attempt to stop Serious Sam. Unlike Zorg Mercenaries, Commanders have some skin left, which is the reason why they are commanders. Having skin also lets them lead Mercenaries into battle, wear underpants and not get blood stains on everything they touch. The Commander gun fires five lasers that are spread out from the center of the gun to create a 110 degree angle spread. This is very similar to the Beheaded Firecracker's attack, but the lasers fired by a Commander do not hug the floor.
- Zumb'uls are large, humanoid creatures from the planet Ras-ad-Nyk and are armed with two plasmarocket launchers. They were trained by Mental in his East Clintwood facility. According to rumor, every Zumb'ul being trained passed because Mental threatened that they would spend the rest of their lives taking pictures of bridges if they failed. Their only attack is to fire two plasma rockets at an enemy. One rocket is fired at the player, while the other one is fired at where the AI believes the player is moving to. The rockets are about as fast as rockets fired by the player. In SSHD, they also have a melee attack, where they hit the palyer with one of their plasma rocket launchers.
- The Fiendian Reptiloid Demon is actually a different species compared to the similarly-named Aludran Reptiloids. The Demon is made from was originally a simple lizard from Fiendia Prime, but was mutated by Mental over several generations to create the Demon. It is one of the few immobile enemies in the game. The Demon's only attack is throwing a large lava ball at the player. This ball is extremely fast and cannot be destroyed. If the ball does not hit the player at first, it will bounce around until it either hits the player or it explodes on its own. Though, the ball can be destroyed using a cannonball or by a few laser beams. In SSHD, it is destructible by all means, yes, even some bullets will do.
- Albino Cyclops are actually modified giant worms from the planet Magnor. Mental added arms and legs to them, but their bodyretracted soon after the body parts were added, making them look very large. Albinos fire homing-orb-shaped projectiles. These projectiles can either be avoided or will burn out after traveling a certain distance.
- The Big Spider is a gigantic cyborg spider. It has two attacks; fire a projectile and hit the player with its legs. The Big Spider's projectile is programmed to intercept the player if the player is strafing a certain direction.
- The Bone Snake fires fast moving projectiles in bursts. It comes in two sizes, regular and large. The large Bone Snake has more health and fires larger projectiles at a faster rate. Despite their looks, Bone Snakes are mobile and will try to hop closer to the player if the player is far away from them.
- Bull Soldiers are demon-like enemies that have two rocket launchers attached to their arms. The rockets are fired one at a time, with each rocket aimed at the direction the player is moving. Once both rockets are fired, the Bull Soldier will have a brief "charge up" period, the fire again.
- The Cerberus was created because of Mental's interest in Ancient Greek mythology and his interest in having a three-headed dog. After gaining some spare time, he created the Cerberus. After being created, the Cerberus began to have problems because each head had its own brain. Mental grew tired of their constant bickering and fighting and decided to remove their brains; instead programming a basic attack sequence into them. Cerberuses will charge the player and attempt to run into them. If it hits the player, it will toss the player to the side in addition to causing damage.
- The Floater is a small and fast flying robot with arms. It can fire a laser or attack the player with a melee attack if the player gets close to it.
- The Flying Kleer is essentially a winged Kleer Skeleton armed with a Blunderbuss. It fires a large fireball from the Blunderbuss. It usually stays away from the player.
- Marcel the Clown was an entertainer that ran "The Wazaro Freak Show". After the show ended, Marcel had no money, so Mental offered to make a deadly clone army outfitted with explosive cakes out of Marcel in exchange for money. Marcel agreed. Marcel's only attack is to use its high speed to quickly get to the player, then explode in front of the player.
- The Martial Arts Master is an actor on the planet Kung Phew. They were modified into deadly flying enemies by chopping off their lets (which were then given to Bull Soldiers) and given the ability to cast deadly dragon magic spells. Unfortunately, their modifications has caused them to continuously sing, so they were given metal masks so that nobody would have to hear them. The Master has one attack; fire a homing Chinese word at the player. This word can be dodged, but will bounce around if it misses until it destroys itself.
- The Martial Arts Zombies are zombies that were modified by Mental to serve as troops on the planet Chi Feng. Their feet have been replaced with metal hooves and they have been given sawblades to throw at long-range threats. The Martial-Arts Zombie has two attacks; throw a sawblade and a melee attack. The sawblade is the Zombie's ranged attack, but it will usually try to get in close and use its melee attack, which propels it towards the player much like the Scythian Witch-Harpy's melee attack does. Merely touching a Zombie will be counted as a melee attack.
- The Orc Gunner is a primitive species that was recruited by Mental. Their best warriors were trained by Mental's forces and given modern armor and weapons. The Gunner's only attack is to fire a powerful rocket from a handheld rocket launcher.
- The Rhino Cybertoy is a mass-produced version of one of Mental's favorite toys. It was given to every family that was under Mental's rule so that they wouldn't rebel. Special types of Rhino toys are equipped with a plasma fuel system and sent into battle. The Rhino Cybertoy has one attack; run toward an enemy until it hits the enemy. If it misses, it will turn back and try again.
- The ScorpSoldier is a scorpion-like enemy that fires a burst of green projectiles at enemies. There are two types of ScorpSoldier; yellow and red. Reds are larger, have more health and do more damage than a yellow one does. There are also bigger red ones that deal a lot more damage than normal red ones, and are more durable.
- The Spawner is a modified Rollerball designed to spawn weak enemies. While it has no direct attacks, the player can be harmed by walking into it.
- The Spider is a cyborg spider that tosses green projectiles. These projectiles are programmed to intercept the player if the player is strafing in one direction. Spiders are frequently seen with Big Spiders]].
- Spiky Bulldogs will charge at the player in an attempt to ram them. If they manage to hit the player, they'll slightly toss the player to another direction and cause damage. If they miss, they'll turn around and try to ram the player again.
- The T-Mech is the sonof the Major Biomech. It swore revenge against Serious Sam after he killed the T-Mech's dad in Serious Sam 1. Originally slated to not be in the game, the T-Mach managed to bribe its way into the game, but only on the condition it got a facelift. In-game, the T-Mech is essentially a copy of the Major Biomech. It will fire one rocket at the player, then fire another a few seconds later. After two rockets have been fired, it will have a cooldown period, then fire the rockets again.
- The Zombie Soldier is an undead humanoid that wields a minigun. This minigun has good accuracy, making it deadly, even at long range. Early on, the Soldier will be placed near the player, but in later levels, the Soldier will be placed far away in order to "snipe" the player from a distance.
- The Zombie Stockbroker is the reanimated corpse of a stockbroker. After the stock in banana ice cream, Mental's favorite snack, collapsed, many stockbrokers committed suicide. Mental decided to raise them from the dead and give them a shotgun in order to repay their debts. Zombie Stockbroker's have only one attack; firing their shotgun. The shotgun has a fairly tight spread, which makes it powerful even at long range.
- Genetically engineered in Mental's Laboratories, there are two classes of Spider Mechanoids. One that acts like a spawning mechanism, simply called "The Mommy," and a smaller, weaker one that is used for infantry. The smaller ones usually attack in groups, as they are born together and will act like one. Their insides are filled with poisonous acid, and the web they eject can be lethal if you receive multiple shots. They are very quick, but the downside is that they have no armour. On the other hand, the bigger ones will be tougher to bring down. Their bodies are waxed with a big layer of ant acid, so every metal object that hits them is soon disintegrated, leaving only small amounts of damage. You'll need a sizable amount of Rockets to bring this one down. Mental, being one of the smartest entities in the universe, got furious when he learned about a "Dead Librarians Society" -- it seems that some of his minions decided to learn how to read and write. Instead of capital punishment, Mental decided to transform those "infidels" into the lowest form of intellect -- barbarians. Librarians,]] actually. Buffed up, "human" monstrosities, equipped with axes and chromed shields which will run at you full speed. The only evidence of their "crazy" youth is their eyes, which each seem to look in a different direction. While reading Sirian, they tried to make sense of the text in question, reading it from left to right and backwards. Too bad no one told them to read it bottoms up.
- After failing to beat Sam, Mental's engineers on Sirius came up with an upgraded version of the Kamikaze soldier. Their motto was: "If you can't make it better, make it bigger," so they replaced two small bombs with one "Sirian bomb of death." Also, in their experiment they noticed that the Life Control Unit (LCU) usually didn't work, so they removed it completely. A spring was added as a joint between Bomb and body to compensate for fast movement. His bomb activates when close enough to the target.
- The Cloned Rifleman is an enemy in Serious Sam 3: BFE. Cybernetically modified clone of human soldier. It is conditioned to blindly attack designated targets. Implanted LCU augments the organic brain and controls high-level functions to obey orders received from Mental's headquarters. Added sensors enable it to see in the dark and fog. Most parts of the skin have been damaged by acid and high temperature, presumably during implantation and other manufacturing processes. Carries standard-issue assault rifle, as used by human forces. Effective at great distances. Cloned Riflemen are one of the most common humanoid enemies encountered in Serious Sam 3: BFE. As their name implies, this variety wield the M29 Infantry Assault Rifle, resulting in them occasionally dropping their weapons when killed, which can supply small amounts of assault rifle bullets. Their attack pattern is unique among all of the enemies in the game, as it depends on their range. At long range, they will fire three rounds before stopping, at medium range they will fire five rounds, and at close range will fire 15 rounds before stopping. Cloned soldiers will also deliver a strong kick if the player is in very close proximity to one. Unlike their shotgun wielding brethren, these soldiers are not handicapped by a weapon which shortens their effective attack range. Though riflemen can attack accurately at long distances, a single rifleman's attacks are weak, but they are seldom encountered alone. A group of riflemen coupled with shotgunners, can be an effective suppressive force despite low damage per shot.
- The Cloned Shotgunner is an enemy in Serious Sam 3: BFE. Cybernetically modified clone of human soldier. It is conditioned to blindly attack designated targets. Implanted LCU augments the organic brain and controls high-level functions to obey orders received from Mental's headquarters. Added sensors enable it to see in the dark and fog. Most parts of the skin have been damaged by acid and high temperature, presumably during implantation and other manufacturing processes. Carries standard-issue shotgun, as used by human forces. Not very effective at large distances, but delivers a strong blow at close range. Cloned soldiers are some of the most common humanoid enemies the player will encounter in Serious Sam 3: BFE. As their name implies, this variety wield the 12 Gauge Pump-Action Shotgun and as a result when killed, will occasionally drop their weapon which can resupply minute amounts of shotgun shells. The pellets from their gun will spread at range, making them less dangerous the farther away they are from their target. Cloned soldiers will also deliver a strong kick if the player is in very close proximity to one.
- The Hatchling Antaresian Spider is an enemy in Serious Sam 3: BFE. They appear in large packs, but are weak enough that one Shotgun blast will kill it. Hatchling Antaresian Spiders are also in cocoons. Their cocoons can be destroyed with one bullet. Usually, when a cocoon is destroyed with a firearm, all nearby other cocoons hatch, spawning more Hatchling Spiders. Most of the hatchling enemies are found in early levels and The Lost Temple of Nubia. The Hatchling Antaresian Spider is a tiny, demon-like spider that can walk on the floor and climb walls. Its primary attacks are to fire acid balls at the distance while getting close to the player. If they get close to the player, they will attempt to bite the player. It can be stomped on by hitting the "E" key when the player is close to the Spider.
- The Juvenile Antaresian Spider is an enemy in Serious Sam 3: BFE. The Juvenile Antaresian Spider is a large demon-like spider, that, like Hatchling Antaresian Spiders, it can walk on walls and ceilings. Its primary attack is spitting acid balls towards the player, but their projectiles can be destroyed with one bullet. As they approach closer, they will attempt to bite the player instead. These spiders serve as main ranged/melee hybrid frontline units or used in small ambushes. They can be encountered in groups of any size.
- The Minigun Turret is an enemy in Serious Sam 3: BFE. Originally develop to cheaply secure remote properties on extraterrestrial colonies, ASU's became very popular companies for EDF forces battling against Mental's horde. XM214-A minigun is the most popular primary weapon for any ASU's, its firepower can stop large waves of smaller enemies without any assistance from the operator. A heavy-duty servo mechanism enables the ASU to quickly refocus between two targets in a fraction of a second. An infrared laser scanner can detect moving targets over an adjustable area of operation. Unfortunately, the simple and robust aiming system is not capable of discerning foes from friendlies, so it shoots at anything that moves. The minigun turret, or ASU 7 Automated Sentry Unit, is one of the least encountered enemies in Serious Sam 3: BFE. These sentries were deployed by the EDF to defend a key point in the city before it was overrun by Mental's horde. They will automatically shoot Mental's horde, Sam or anyone else due to their system not being able to recognize friendlies and foes. They are armed with a Minigun which is deadly due to its speed and firepower. They will search for anything that moves with their laser sight. They cannot be destroy by any weapons at all and can only be deactivated by a switch.
- The Aurigan Cave Demon is an enemy in Serious Sam 3: BFE. The Aurigan Cave Demon, "Cave Demon" for short, or "Space Monkey" by sam, is the most atypical enemy in the Serious Sam series. It does not charge at the player like most enemies do, but instead lurks on columns, waiting for its opportunity to leap towards the player and attack. If there are no columns around, then they will instead latch onto walls or jump onto the roof of buildings. They can leap great distances as well.
- The Adult Arachnoid is an enemy in Serious Sam 3: BFE. The Adult Arachnoid is a lot similar, appearance-wise, to its adult classic counterparts, but with a mouth on the bottom part of its body, yields 2 guns, possibly chain guns and within its pincers. It also seems larger than classic Adult Arachnoids. The first Adult Arachnoid appears as a boss in Into the Spider's Nest. Subsequent Adult Arachnoids serve as harassment units, providing supporting fire to the other units. Unlike classic counterpart, most of the arachnoids are located in the ground level as opposed to rooftops and columns. Most of the arachnoids appear in groups of one to two and in places where it's possible to take cover. It has a different attack pattern compared to its classic counterpart, which shoots decently-damaging bullets at a rather average rate, this Arachnoid shoots low-damaging bullets at a very fast rate. It opens its pincers, and starts shooting a burst of 20 bullets per hand (40 in total), then stops, and repeats that sequence after a short interval. Compared to classic counterpart, it is also faster and can often avoid slower projectiles. The miniboss version's bullets can pierce through the debris the player is probably hiding behind, destroying them. It also has roughly three times as much health as its normal counterpart.
- The Hatchling Arachnoid is an enemy in Serious Sam 3: BFE. Hatchling Arachnoids are newborn Arachnoids. Since they are still developing, they cannot wear armor plating nor have miniguns built into their arms, like their adult counterparts have. To compensate for the lack of built-in miniguns, the Hatchling has one of its arms cut off and replaced with a minigun. A major weakness is that their necks have not fully developed yet, so one can snap it with enough strength, instantly killing the Hatchling. Hatchlings can also deliver a powerful sting if they are within very close proximity to the player. Hatchling Arachnoids are smaller and weaker versions of Adult Arachnoids, but in groups, they can pose just as much threat as an Adult one would. What makes them even more dangerous is the fact that they can walk over debris, such as rumble. They follow the same attack pattern as their adult counterparts do; when they spot the target, they will open fire with their minigun, then stop, wait a few seconds, and fire again. its neck can be snapped by being next to it and hitting the E key. This instantly kills it.
- The Scrapjack Rocketeer is an enemy in Serious Sam 3: BFE. Conveniently named "scrapjacks", they are low-grade models of Mental's forces, created from sewn-together parts salvaged from KIA units of various other models. This particular variant carries two rocket launchers. If left unattended, they are dangerous because of their firepower. They are not built very sturdily so they can be disposed of easily. With three selectable heads to choose from depending on the situation, it can exhibit different behaviors. Ranging from bland attacking to berserking rage. They start to appear from the level Unearthing the Sun. They're usually present one to few at a time, although there can be more in the final level. They mainly serve a role of giving support to the main attacking force. Scrapjacks are strong enough to survive multiple direct rockets, but can still be easily dispatched at a distance with concentrated fire from an assault rifle, and even more easily eliminated by detonating a single block of C-4 Explosive that has been attached to the torso. Their firing patterns are very similar to the Zumb'ul, a Scrapjack will fire a rocket where the player currently is, and another where the Scrapjack predicts where the player's estimated direction is. The Scrapjack also has a "berserk" mode when it has been attacked enough. In this phase, the Scrapjack will rapidly fire missiles in a much faster, and longer succession just as accurately as regular attacking. Scrapjacks also have a strong melee attack if the player gets too close. Unlike most enemies, the Scrapjack can only be executed with a melee attack if it becomes stunned under heavy fire from various weaponry. Not all weapons will stun the Scrapjack, however most strong ones such as the AS-24 Devastator, and the Rocket Launcher will always stun the Scrapjack under consistent fire. A special melee attack against the scrapjack consists of the player ripping off the head of a scrapjack, which is then followed by a kiss on the resulting trophy the player is left with.
- The Khnum is an enemy in Serious Sam 3: BFE and a boss in the Serious Sam HD: The Second Encounter and its DLC The Legend of the Beast. The Khnum is a large, aggressive creature that comes from the distant planet Arietis Lambda, where it is worshiped by smaller creatures as a god. Although not divine in any way, its thick skin and regenerative abilities make it appear to be immortal. The name Khnum, comes from an ancient Egyptian god due to their ram-like head. There is no apparent explanation why they are working with Mental's forces. The Khnum is a very large, bipedal creature, standing approximately forty five feet tall. Its thick, grey skin and immense muscle mass make it both durable and powerful. Its head features red eyes, a gaping mouth showing razor teeth and two prominant horns similar to a goat, but not practical for use as a weapon. They do not have feet, rather they have two large hooves that, while slow, allow it to walk as fast as Sam. They do have hands, each with three fingers and what appears to be an opposable thumb, which they use to conjure fireballs. The Khnum appears early in the game as a passing feature, looking at the player but does not engage, as if disinterested. Later, it emerges after Sam activates the first Time-Lock generator, Horus. The first encounter with it takes place in a relatively narrow corridor with pillars that can be destroyed and a crate of C4 Explosive, which can help defeat it when no other explosive weapon may be available. Subsequent khnums appear most commonly alone or in pairs with groups of enemies. However, in the final level, several can appear at the same time. They usually appear with larger amount of weaker enemies.
- The Technopolip is an enemy in Serious Sam 3: BFE. The Technopolip is what happens when an unknown polyzoic creature hijacks an Apache helicopter. The creature itself appears to have unknown origins. However, its ability to hijack mechanical devices suggests that it was tampered with by unknown forces at one point, most likely Mental. The polyzoic creature is able to repair the vehicle it has hijacked, making it impossible to damage without explosive weapons due to the helicopter's armor and the Technopolip's regenerative abilities (although it doesn't regenerate health in-game at all). Two Techopolips can be seen flying by through the roof in the main atrium in the Into the Spider's Nest, but the first one Sam has to fight shows up as a boss in No Place To Hide. Afterwards, it appears sparingly, usually one or two at a time. The Technopolip's only attack is to fire the helicopter's machine gun at a target but during the battle against Ugh-Zan IV, it fires rockets instead of machine gun. At first, the burst of the machine gun has low accuracy, but will become more accurate after a few rounds are fired off. It can only be harmed by explosive weapons, such as the XPML21 Rocket Launcher or AS-24 Devastator. Its AI is advanced enough to avoid slow projectiles. However, it will not move while it is firing its machine gun.
- The Sand Whale is an enemy in Serious Sam 3: BFE. The Sand Whale is a large, worm-like creature that lives in the sands of Egypt. It is unknown if it is part of Mental's forces, as it was brought to Earth as a larva from Gamma Pegasi, probably due to landing-pad contamination. It is very territorial and can sense something walking above the sands from miles away. When something gets close to it or its territory, it leaps out of the sand and swallows the thing whole. Its thick scales make it immune to all sorts of weapon known to man, except for precision nuclear strikes. The Sand Whale's purpose is mostly to keep players from wandering off the level in large, open-ended levels. If the player gets too far from the level, the Sand Whale will start growling and shake the ground. If the player continues to go away from the playing area, the Sand Whale will suddenly appear and eat them. They also sometimes randomly appear, diving in sand and probably devouring some random prey, far in the background. The player does not fight it, nor does he have the firepower to destroy it, but ultimately you can use it to help you defeat the final boss, as Ugh-Zan IV sometimes walks up to sand, and growls, calling the Sand Whale to fight it.
- The Witch-Bride of Achriman is an enemy in Serious Sam 3: BFE. The Witch-Brides of Achriman are female, human-like aliens from an unknown planet. She was originally a sorceress of The Grand Council, but was tricked into serving Mental by Arhriman, the Lord of the Shadows. Now, she is trapped between the real world and the world of the shadows. With dull purple skin and six tentacles protruding out of her back, a Witch-Bride of Achriman are of regular human size. Despite their appearance, they prefer to keep their distance, using powerful psychokinetic attacks and warping space to protect themselves. Between attacks, a Witch-Bride will phase out of reality and move to a different location nearby. She can also use her tentacles to deflect incoming attacks including bullets and explosives, which detonate harmlessly in front of her. A Witch-Bride of Achriman has but a few attacks. She can inflict crushing damage with her powers from afar which does minor damage over a short period. Her second attack is a powerful ranged telekinetic grab that will pick Sam up and crush him, doing moderate damage and restricting aim speed.
- The Alcor Class Warship is a boss in Serious Sam 3: BFE. The Alcor Class Warship is the most basic spaceship used by Mental. It is designed to deploy troops and to serve as a "ground-scorcher" with its laser beam, which is able to burn through steel plating at the rate of one foot per second. It uses a FTL system to quickly reach locations. The ship is able to resist any small arms fire and anything up to a strategic missile. However, it has one significant weakness; the hatches used to teleport troops in are unguarded, allowing someone on the ground to damage it with rockets, or other projectile-based weaponry. If the ship has suffered significant damage and its systems are in danger, the onboard AI will retreat via a short-range jump before the ship can be destroyed. The Alcor Class Warship primarily attacks with a continuous laser beam from the center of the ship's underside. Depending on the damage taken, the Warship can multiply the amount of laser beams, allowing for a maximum of three possible beams to scorch the nearby area. Its second indirect way of attacking are the hatches located on both sides underneath the Warship; when each hatch is opened, a teleport beam will spawn various enemies in different spots of the battlefield. These exposed hatches also serve as the Warship's only weakpoint, the Warship will take damage if an open hatch is shot with explosive weaponry, or other projectile weapons. Each hatch can only sustain a certain amount of damage before automatically closing. The amount of hatches opened appears to be based on the damage the Warship has sustained, opening the most hatches when it is nearly destroyed. The Warship appears in the first level of the game, Summer in Cairo, where it destroys an entire building with ease before teleporting away. Later, the player will fight it in two levels, Under the Iron Cloud and The Power of the Underworld.
- In Serious Sam 3: BFE, there are many propaganda postes located throughout the campaign, usually featuring Gnaars or Beheaded Kamikazes on them.