Cthulhu

This spell costs {b}{b} less to cast if an opponent's
creature died this turn.
When Cthulhu enters the battlefield, draw a card.
Annihilator 1
When Cthulhu dies, exile it with an Immortal
counter on it.
{4}, Remove an Immortal Counter from Cthulhu: Return Cthulhu to the battlefield. Activate
only as a Sorcery.