Level up your Heroes to increase their powers. Levelling up your heroes increases their stats (attack, health, defense points), including their Special Skill and maxing the level for ascension.  
A Hero can be levelled up by:
  1. Go to your Hero Roster by pressing Heroes icon at the bottom of your screen
  2. Select a Hero from the Hero Roster
  3. Press “Level Up”.
Levelling up a Hero requires sacrificing other Heroes (and a little food, your heroes get hungry!) The number of Experience Points (XP) and food needed to level up the Hero is specified on the “Level Up” screen. 

A Hero’s stats, as well as the chance to power up its Special Skill, will become higher if Heroes of the same colour are sacrificed when leveling up.