Arma 2: DayZ Mod is a free multiplayer modification for Arma 2 and Arma 2: Operation Arrowhead developed by Dean Hall.
DayZ is an open-world survival horror set in a post-soviet state of Chernarus. The population of a country has turned into zombies due to an unknown cataclysmic event. The players have to survive in a hostile environment evading enemies and searching for supplies, weapons, and ammunition in abandoned buildings. Other players and zombies are not the only dangers in DayZ as the game features a complex player health system. It is crucial to control hunger, thirst, traumas, and illnesses. Death in the game is permanent. If the player dies, one has to create a new character and scavenge for supplies from scratch.
The modification puts a heavy emphasis on realism as the environment is interactive and has various effects on the player. It is easy to break your character bones and even fracture them. Your character can go into shock after surviving several bullet wounds or getting bitten on by a zombie. Infections can be received from zombies or the bodies of other players. It is also possible to faint due to blood loss.