Evolution is a unique skill exclusive to your all your hired heroes. It is essentially a prestige for your hired heroes.
At level 1000, you are given the choice to reset your hired heroes' skills AND keep the levels and in doing so, add a massive DPS chunk.
You will know a hero is evolved because:
- An evolved hero is marked with a golden frame.
- An evolved hero can be continue being leveled as if 1000 was 0. (They will automatically be levelled to 1001)
- An evolved hero loses all his/her/its skills, but can be repurchased at their respective equivalent levels. (i.e., skills would be available at levels 1010, 1025, 1050, and so on)
The main reason Evolution is so helpful, is that you can keep advancing in the later stages of the game when new heroes are blocked by a large gold gaps (For example, hh to kk gold) by evolving earlier heroes.
NOTE: You do NOT keep evolutions when you yourself prestige.