Avatar Yangchen

+1: You gain life equal to the number of creatures you control plus the number of planeswalkers you control.
0: If you have at least 15 life more than your starting life total, exile Avatar Yangchen and each creature your opponents control.
-2: Create a 2/2 white Airbender Monk creature token named Air Nomad with "Whenever you gain life, put a +1/+1 counter on Air Nomad."