As you use your Heroes to beat Campaign, PvP and PvE raids, they’ll earn Hero XP. Once their XP bar is full you’ll be able to level them up, upgrading their stats and progressing towards Ascension milestones. 

Collect Hero Shards from lootboxes, quests and buy them from the Shop to Ascend your Heroes to higher tiers! 

You can see how much XP your Hero earned after a raid in the post-raid screen.

You can also get Hero XP Potions from the Shop to replace missing XP and level up your Heroes faster!