Each Hero automatically generates XP for themself for each subsequent round they are on the map, leveling themself up after achieving enough XP to reach the next level. Heroes start at Level 1 when placed (or Level 3 with Empowered Heroes, and/or the Extra Empowered Relic from Contested Territory), and can level as high as Level 20. Levels provide big boosts in power for the hero, providing a variety of additional benefits for the player's defenses. Some heroes level slower than others. If multiple heroes are on screen, they share XP equally among each other.