You can unlock Champions by "mastering" (or 100% completing) the current Champions you have unlocked. Do this by using their power-ups in a match. Once your current Champions are completed, a new Champion will appear!
You can unlock Champions by "mastering" (or 100% completing) the current Champions you have unlocked. Do this by using their power-ups in a match. Once your current Champions are completed, a new Champion will appear!