The Abyss Watchers

First Strike.
When The Abyss Watchers enters the battlefield,
each opponent creates a 3/3 Black Undead
Warrior Creature token named Watcher.
When this creature dies, exile it with a cinder
counter on it. If this creature is exiled with a
cinder counter on it, and there are no creatures
named Watcher on the battlefield, return it to
the battlefield transformed.