Unending Nightmare

Bloodthirst 1 (If an opponent was dealt damage this turn, this permanent enters the battlefield with a +1/+1 counter on it.)
Wither (This deals damage to creatures in the form of -1/-1 counters.)
Persist (When this permanent is put into a graveyard from the battlefield, 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.)