By earning XP Tokens, players are able to spend it on levelling up their Champions. Levelling them up increases their health, abilities, and attack damage. Each level costs more XP Tokens than the last. Each Champion can be levelled up to Level 20.
Different Champions will also start at different star amounts. A Common Champion starts at 1, Rare at 2, and both Epic and Legendary Champions at 3.
By earning more duplicates of a Champion, and using some Glory, you'll be able to upgrade their star rating. Upgrading them will increase their current abilities by a multiplier on top of their level. Every Champion can be upgraded up to 5 stars.