King Tutkluck, the Acorn God

You ay sacrifice this creature when it enters the
battlefield. If you don't, during your endstep, if
you don't control the Acorn, you lose the game.
Flying, forestwalk, swampwalk, deathtouch, indestructible, hexproof, haste, trample.
When Tutkluck deals combat damage to a player, create the Acorn, a legendary artifact with "You
win the game."