Zombie Union featured a different gameplay in comparison with previous zombie modes. There is no infection spreading, instead, zombies now can choose to cooperate with either Counter-Terrorist or Terrorist team. It can be set to either Team Deathmatch or Original (Annihilation) sub-mode. It follows the main settings of those sub-modes: each team have to reach a certain amount of points or rounds, depending on the selected scenario to play in, with the addition of new items, skills and special rules.
There are 15 items available for this mode. The items can be used after the player got it from supply box.
|Speed Up||Increases the movement speed for a short period.|
|Infinite Grenade||Unlimited grenade usage for several seconds (Human only).|
|Invincibility||Becomes invulnerable for several seconds.|
|Jump Up||Jumps higher for a short period.|
|Shooting Up (Unused/Removed)||Increases the accuracy of teammates for a short period (Human only).|
|Team HP Recovery||Heals self and teammates by 50% of their maximum health (Automatically activated when picked up).|
|Landmine||Lays down a landmine to damage an enemy that walks over it.|
|Nuclear Bomb||Releases a nuclear bomb that is capable of wiping out both enemies and allies.|
|Self Destruct||Releases a powerful shockwave to temporarily stun nearby enemies and allies including the player.|
There are 25 compatible maps:
- In this mode, zombies have higher resistance against stun and knockback.
- Zombies can only heal 100 health points when regenerating health.
- Zombie Grenade deals approximately 100 damage.
- Zombies are greatly stunned by any kind of explosives (with the exception of Nuke which only knocks the zombies away).
- Terrorists will be depicted in red while Counter-Terrorists in blue for both zombies and humans.
- Landmines does not trigger detonation when the deployer steps on it, but a teammate or enemy still triggers it.
- If a landmine does not detonate in a period of time, it will disappear.
- The landmine damages both enemy and the deployer, if both are caught in the explosion radius.
- While landmines don't damage your teammates' health, their armor will be decreased instead.
- Invicibility does not protect the user against damage over time or 'Enemy HP Down'. It does however, protect them from the stun effect (if the user is using a zombie) or any other projectile or melee attacks.
- Zombies under the effect of Strong Lifepower will have their maximum health increased by 500 and their maximum armor points will be increased by 50.
- In this mode, Voodoo Zombies are able to cast a debuff whenever they hit an opponent called [Curse] which disallows the victim from using any skill or item. They gets points by healing their teammates.
- Friendlies and yourself will have some sort of "ring" orbiting around.
- If you point your crosshair at your teammates an icon will appear indicating not to shoot or attack.
- 'Shooting Up' item exists in the .nar files. However, it was cut and doesn't show up in-game.
- Venom Guard and Sting Finger have better stun resistance than any other zombies.
- This mode is not available in the Singapore/Malaysia, Vietnam regions and Counter-Strike Nexon: Zombies.