Night King

Indestructible, Intimidate
Whenever a creature enters a graveyard from the battlefield, return that creature to the battlefield under your control. It loses all abilities. Creatures you control are black zombies in addition to their other types and can't attack unless it is Winter. When Night King leaves the battlefield, sacrifice all zombies.
If you control ten or more snow permanents, you may tap them. If you do, it becomes Winter. It becomes Summer when those permanents untap.