Szarel, Genesis Shepherd + Phyrexian Altar

Szarel, Genesis Shepherd

Phyrexian Altar

How it works

1. Activate Phyrexian Altar by sacrificing a persist creature without a -1/-1 counter on it.
2. When the persist creature dies, its persist ability and Szarel trigger.
3. Resolve the Szarel trigger, putting a number of +1/+1 counters on the other persist creature.
4. Resolve the perist creature's trigger, returning it from your graveyard to the battlefield with a -1/-1 counter on it.
5. Repeat.