The Chaos system is a core mechanic in Dishonored, influencing the game world and its ending. Killing enemies, especially civilians, and being detected frequently increases your Chaos level. A high Chaos playthrough results in more guards, more rats, and a darker, more pessimistic ending. Conversely, a low Chaos playthrough, achieved by non-lethal takedowns and remaining undetected, leads to a more hopeful outcome. The game tracks your Chaos per mission, and the overall Chaos level is an average. Consider your playstyle carefully!
