Ulos, the Nether Step

Indestructible
When Ulos enters the battlefield, your life total becomes 0. Your life total can't be more than 0 and you don't lose the game by having 0 or less life. When Ulos leaves the battlefield, your life total becomes equal to Ulos power before it left the battlefield.
Whenever Ulos takes damage, exile it. Return it
to the battlefield at the beginning of your next upkeep.