Certain cards, called monster enhancers, raise or lower the combat strength of individual monsters. (Penalties to monsters are still considered enhancers.) They also affect the number of Treasures the monsters are worth.
Monster enhancers may be played by any player during any combat.
All enhancers on a single monster add together. If there are multiple monsters in a combat, the person who plays each enhancer must choose which monster it applies to.
Exception: Anything that enhances a monster also enhances its Mate . . . if Ancient, Enraged, and Mate are played on a single monster, in any order, you are facing an Ancient Enraged monster and its Ancient Enraged Mate. Good luck . . .