There are five known types of enhancements in City of Heroes: Training Enhancements (TO), Dual Origin Enhancements (DO), Single Origin Enhancements (SO), Trial Reward Enhancements (TR), and Hamidon Enhancements (HO).
Enhancements are broken down into two categories: offensive and defensive. Offensive enhancements offer a greater bonus that defensive enhancements.
Value of Enhancements TO: 8.25%/5% DO: 16.5%/10% SO: 33%/20% TR: 25%/15% (affects multiple aspects of a power) HO: 50%/30% (affects multiple aspects of a power)
Effect of Level The level of the enhancement does no directly affect the benefit of enhancements. However, the level of the enhancement relative to the level of the hero does. An enhancement that is one level higher than the hero using it has a +10% bonus to the enhancement's base bonus. A level below is -10%. This works us to three levels. Example: a level 35 enhancement used by a level 32 hero has a 42.9% bonus.
