Light Yagami

0: Sacrifice a planeswalker, you may move any number of loyalty counters from it to Light Yagami.
-X: Light Yagami deals X damage to target creature or player. This ability can be used as many times a possible whenever you could cast an instant.
-20: Sacrifice all permanents, put a loyalty counter on Light Yagami for each permanent sacrified this way. You and permanents you control phase out.