Enabled at Lv 15
All heroes can get EXP to be upgraded from the quests, beside which you can consume EXP items and Silver to upgrade them.
Enabled at Lv 26
You can equip your hero with Relics and thus to evolve the hero and improve the quality of the hero. The Evolved hero can get all attribute bonus of the Relics consumed.
Each hero of each quality can be equipped with 6 Relics. The equipped Relics can’t be unequipped. Every time you equip one Relic, the hero’s attributes will be boosted. It requires 6 Relics equipped to evolve the hero. When the hero is evolved, she will get new skills.
Note: The character’s skills should be unlocked by Starsoul.