- See Human for its counterpart.
Zombies were created when the Rex Research Institute were experimenting on living things. They later escaped from the laboratory and started infecting other humans. They were first seen in Abyss, the later in other maps. During the chapter Chaos, they managed to escape to the surface and infected the people in Habana Vieja. Dr. A was seen being chased by a zombie after the Rex Virus Incident.
Differences between Origin and Host Zombies
A common misconception  among players are the [Origin] and [Host] zombies. At the start of each round, either one or two players, depending on the amount of players joined, would be chosen as the zombies.They would be [ORIGIN] zombies NOT [Host] zombies. Only the Singapore/Malaysia and Indonesia region is known to make such an error.
- [Origin] Zombies – They are the players chosen to be zombies at the start of each round. They used to be scientists, and were gradually infected with the Rex Virus.
- [Host] Zombies – They are the devolution of the [Origin] Zombies. These zombies are similar to the Origin Zombies except that they used to be the humans  who had been infected by another zombie.
After 20 seconds of the round, one or two of the players are chosen to become an Origin zombie (This depends on the number of players). The Origin zombie must infect all of the other humans by its claw. Infected human will turn into host zombies and must attack other humans. Zombies are considered the winner of the round if all humans are infected. In this mode zombies can't envolve and no HP regeneration.
New types of zombies have been released in this mode; Light zombie, Heavy zombie, Psycho zombie and Voodoo zombie. They will also gradually start to infect the surviving humans. They have new abilities that can regenerate their HP and evolve with the blood of humans. The origin can now execute their abilities whereas the host can't.
New playable characters are released: Hero and Heroine. These characters each hold exclusive weapons that only they can use and are meant to kill zombies (SVDEX for Hero and Quad-barreled shotgun for Heroine). The zombies are able to revive unless a headshot is inflicted upon them. However, each zombie killed will increase surviving humans morale, thus increasing their strength by 10%. This increment applies to all humans. New zombies are also released: Deimos and Ganymede.
There are several new features introduced in the new update applied to Zombie Mutation and Zombie Hero:
- Salamander - A flamethrower that can burn enemies in close range and it can set the enemy on fire for several seconds. However, its attack range is low and it cannot be fired in water.
- Requiem - A new map introduced takes place in a ghost town.
- Rest - Another map introduced takes place in an abandoned church.
- Origin - A zombie map takes place in a tomb.
- Banshee - A witch that turns into a zombie. Can confuse humans with her grenades and sends a group of bats to pull the targeted human to her.
- Stamper - An undertaker zombie that is able to place an Iron Maiden that can reduce human's movement speed, act as a defensive shield and can jump on it.
- Jiang Shi - Chinese zombie that is exclusive to China regions. It shares the same performance as Ganymede.
- New weapon
- M32 MGL - A light weight grenade launcher, fed with 40×46mm grenades, a revolver-style semi-automatic grenade launcher with 6 slots.
- New map
- Forbidden - A new map that takes place in an abandoned factory.
- New zombies
- Sting Finger - A female researcher that turned into a zombie.
- Venom Guard - A security guard turned into a zombie.
- New items
- New weapon
- M2 Browning - Portable heavy machine gun fed with 250 rounds of .50 BMG. Its firepower is superb due to its high caliber used.
- New map
- Dark City - A new map that takes place in an abandoned city.
- New zombie
- Night Stalker - A powerful zombie that only appeared during the night.
- Darkness Supply Box - Collect to obtain variety useful items.
After 20 seconds of the round, AI-controlled zombies will start to appear and attack humans. Unlike Zombie Mods, the player does not turn into a zombie after being attacked but decreases their health points instead. The players must survive the round in a certain amount of time to win or reach to a certain point in the map. At the end of some maps, the player must defeat a boss to win.
Zombie: The Union
The zombies are divided into 2 teams, Counter-Terrorist and Terrorist. Zombies in each team will help the humans engage the opposing forces.
The zombie team must infect all humans or prevent them from reaching the escape zone.
- Blood Castle: Prevent the humans from escaping by using a hovercraft.
- Skyline: Prevent the humans from escaping through a cargo truck.
- Venice: Prevent the humans from escaping via Osprey.
- Hitchhiking: Prevent humans from escaping by using a train.
The first generation zombie that is code-named as 'Normal type'. This specimen has balanced aspect of movement speed and knock back resistance against human attacks. It has the ability to berserk where the movement speed will be greatly increased and the knock back resistance is very high.
An abomination created by Dr. Rex, this zombie is code-named as 'Light type'. This specimen boasts fast movement and good jumping ability but is vulnerable when attacked. The Light Zombie host possesses the ability to turn itself invisible.
An abomination created by Dr. Rex, this zombie is code-named as 'Heavy type'. This specimen is excellent for breaking humans' defensive line, and can absorb some of damage taken. The Heavy Zombie host has an ability to pull out a device inside its body that can be used as a trap that slows down any humans caught in it.
This zombie was originally a co-worker biologist of Dr. Rex, when it was a human. He turned into a zombie in an accident, earning the nickname of 'psycho type'. The Psycho Zombie host have the 'Smoke' skill that screens an area with thick smoke.
These magicians are infected by the Rex Virus in their own wills to obtain stronger magical power. They have abilities to cure team members with strong magical power and also curse enemies to stop them to use item and skills for a certain period of time.
A special zombie that started to appear in a large scale since Prototype Phobos has been discovered. Its DNA has been identified as the similar type as Phobos. This zombie is strong and powerful as it possesses most of the advantage that the current discovered zombies own. It has a skill to drop enemy's weapon with a long distance attack or make them unable to attack for a period of time.
No one have seen Banshee before, only a ancient rumor about her. According to the rumor, Banshee is a witch zombie that is put to death by leading the heathen group. It uses magic type ability to create confusion and has the ability to capture a target from a long distance.
There is a rumor that a torture expert corpse in some part of Europe has revived as a Stamper and is going around killing people in a much cruel way than he was alive. He carries torturing equipment on his back to use it for various purpose.
String Finger is a female Researcher who turned into a zombie due to Z-Virus while working for an Unidentified Illegal Research Complex. With her elasticity ability, she is able to penetrate through enemies in an instant with a sharp tentacle and high jumping abilities.
Venom Guard is a male Security Guard who turned into a zombie due to Z-Virus while working for an Unidentified Illegal Research Complex. Its body has been filled up with toxic substance as it was affected by chemical waste. It has the ability to harden its body and heal injuries.
- ↑ A view or opinion that is incorrect because based on faulty thinking or understanding.
- ↑ The players