Rage is used when using skills. Each skill has a set amount of rage. The maximum rage you can have at a time is 150, and all rage is lost when you return to a non-combat area (such as the city). Each player no matter what class has a maximum of 100 rage. When you obtain a Eudaemon and upgrade its passive skill Fury Master to level 5, you obtain an extra 50 rage. 10 for each level of the skill, starting at plus 10 rage at level 1.