Chaos is one of the most important features of Dishonored and can transform the story and environments & How Corvo's Quests unfold.
Chaos is calculated throughout each mission based on Corvo's actions and decisions. At the end of the mission your score is added up and will either be high or low chaos. It is not just a case of killing.
Below is a list of how to increase your chaos score in order to achieve High Chaos .
Assassinate Mission Targets - Greatly Increases Chaos Score
Assassinate Secondary Targets
Murder Guards - Every 3 guards killed increases Chaos score.
Murder Civilians - Killing 1 civilian is the equivalent to killing 3 guards
Weepers - Every 4 Weepers killed increases chaos score
Alarms - Triggering at least 4 alarms in a level will greatly increase Chaos score
Body discovery - Every 4 bodies discovered increases chaos score
Tallboys - Every Tallboy destroyed increases chaos score
Poison SlackJaws Grannary
Rewire Walls of Light/ Arc Pylons (rather than unpower)
Create havoc - use your gun, grenades & powers make noise to attract guards.
Make saves throughout a level. At the end when you get your score if it says Low Chaos just reload a previous save rather than replaying the entire mission.
Tips: Body discovery, Civilian deaths & Alarms really help increase your chaos score. I got low chaos on Boyles Party with 40 kills. When I replayed it I got 35 kills but the body discovery and civilian death count was much higher, Despite having less kills I got the High chaos rating. Try and vary your weapon kills, melee & crossbow are great for low chaos runs but not for high chaos.