Dvarki, Labyrinth Master

Wither, Planeswalk (If this creature would leave
the battlefield,
instead exile it with a planar counter on it
for each creature you control.)
Whenever a creature dies, if this creature is in
exile, remove a counter from this creature.
Then, if there are no counters on this
creature, return this creature to the battlefield
as a copy of a creature on the battlefield.