Duo, The Merciless

Flying, Vigilance, Lifelink

At the beginning of each end step, for each player who cast a spell that turn, create a colorless XP token with
"{t}{1}: Sacrifice this token. Scry 1 and then draw a card."

Sacrifice 5 XP tokens: Add 5 mana in any combination of colors

Sacrifice 10 XP tokens: Tap target creature and put a stun counter on it.