A sub system in which you can evolve your heroes to a higher rank.
Evolving your hero will provide 1 skill credit each rank
Each rank will also allow you to train 1 static skill
Evolving your here will require 50*rank Evolution Essence (ie. rank 1 will cost 50*1=50 Essence, rank 5 will cost 50*5=250 Essence)
Evolution Essence is available as rewards in Electrum Mine Runs and will be added to other areas of the game over time
In a future update, heroes will become tradable, it is very likely that a hero will require a certain rank in order to be eligible.