25 янв. 2021, 22:0525.01.21
You do it in the tavern. The character has to be at the max level for that rank and you have to sacrifice a certain amount of characters (or chickens) of the same rank.
So for example if you wanted to take a champion from rank 3 to rank 4, you would have to get that champion to level 30 and then sacrifice 3 other rank 3 champions.