The NPCs act as if they really are alive, having different states, such as task accomplishment, combat, rest, feeding and sleep. The monsters in the game also act in this way. These monsters will move in large groups. The non-scripted way the characters work means that there are an unlimited number of random quests. For example, rescuing Stalkers from danger, killing Stalker renegades, protecting or attacking Stalker camps or searching for treasure. The AI characters travel around the entire zone as they want.