Imseti, Guardian of the Dead

Other Zombies get +1/+1.
Whenever a creature you control enters the battlefield from your graveyard, it enters with an additional +1/+1 counter.
Undying(When this creature dies, if it had no
+1/+1 counters on it, return it to the battlefield under
its owner's control with a +1/+1 counter on it.)