Zumb'uls are large, humanoid creatures from the planet Ras-ad-Nyk. They are armed with two plasma rocket 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 player with one of their plasma rocket launchers.
Zumb'uls are mainly encountered alone or in pairs, mostly supporting other enemies. There are a few instances in later levels where several of them can be encountered at the same time. Most zumb'uls are found guarding entrances or are located in elevated places such as pillars.
- A Zumb'ul's rockets can be jumped over, which is useful for situations where the player doesn't have enough room to dodge the rocket, but can jump over it.
- Zumb'uls are a major problem when dealing with other enemies; their projectiles are large and fast, making them difficult to dodge if the player isn't paying attention. They should be one of the first targets taken out in a group, especially if there are more than one of them at once.
- Zumb'uls in higher places such as rooftops are more dangerous as it is harder to avoid the splash damage of their rocket hitting the ground.
- The RAPTOR Sniper Rifle is particularly useful against the Zumb'ul; one zoomed shot can kill it, making the RAPTOR the best weapon to use against medium or long range Zumb'uls.
- Groups of Zumb'uls can quickly be killed with either the XM214-A Minigun or XPML21 Rocket Launcher, as they both have high rates of fire, allowing them to quickly inflict damage.
- The SBC Cannon is very useful if Zumb'uls are lined up so that multiple Zumb'uls can be killed with one cannonball. However, using it on one is waste of ammo.
- Do not approach Zumb'uls too closely in SSHD; they have a melee attack.
- In Croatian (Serious Sam is a Croatian game) "Zumbul" means hyacinth and "Rasadnik" means a nursery garden. So it actually means a hyacinth from a garden.
- In Classic Serious Sam, the colour of the rockets are blue while in HD they are red.
- The Zumb'ul is similar to the Mancubus from the Doom series.