Hexavus + Phyrexian Altar

Hexavus

Phyrexian Altar

How it works

1. Activate Phyrexian Altar by sacrificing the persist creature, adding 1.
2. When the creature dies, its persist ability triggers, returning it from your graveyard to the battlefield with a -1/-1 counter on it.
3. Activate Hexavus' second ability by paying 1 and removing the -1/-1 counter from the persist creature, putting a +1/+1 counter on Hexavus.
4. Repeat.