Divinity

The "divinity" of a hero is a concept similar to "rarity" in other games. There will be 4 divinities: Common, Special, Epic and Legendary. The higher the divinity, the higher base stats are gonna be, on average. Epic and legendary heroes are mythological characters, so their frequency of appearance is very low, and they are very valuable. To distinguish the divinity of a hero, just look at their frame.