Head over to command
Open up heroes
Scroll down to defenders
Press X on your selected hero and again on upgrade/inspect
Hit Triangle until your defender reaches level 10 (this requires around 6 or 7000 hero XP)
Once you hit level 10 you will be given the option to evolve your defender
Once you hit evolve you will be given a list of items required to evolve your defender and once you have aquired those you can evolve your character and earn this trophy