- See Abyss2 for the continuation map.
Operation Abyss (zm_abyss) is an official Zombie mode map in Counter-Strike Online.
While conducting a mission in the B-2 area of Rex Laboratory, some members of the mission team fell into the B-1 area due to a C4 explosion. What they found were sealed subjects of a failed study. Unfortunately, the sealed subjects have been awakened by the explosion...
- Humans: Survive the Zombie attacks until reinforcements arrive. Watch for fellow comrades who may turn into Zombies. You are authorized to kill all Zombies.
- Zombies: Those who have turned into Zombies must kill the Humans and turn them into Zombies. Zombies have higher HP and faster speeds than Humans.