Phyrexian Altar + Host of the Hereafter

Phyrexian Altar

Host of the Hereafter

How it works

1. Activate Phyrexian Altar by sacrificing the persist creature that has a +1/+1 counter on it, adding one mana of any color.
2. When that creature dies, its persist ability and Host of the Hereafter trigger.
3. Resolve Host of the Hereafter's ability, putting at least two +1/+1 counters onto the surviving persist creature due to the counter-increasing effect.
4. If that creature had a -1/-1 counter on it, remove that and one of the +1/+1 counters from it as a state-based action.
5. Resolve the persist ability from step 2, returning the persist creature from your graveyard to the battlefield with a -1/-1 counter.
6. Repeat.