Prerequisites
- Solemnity on the battlefield
- Phyrexian Altar on the battlefield
- If a persist creature is used, it does not have a -1/-1 counter on it
- Otherwise, if an undying creature is used, it does not have a +1/+1 counter on it
Steps
- Activate Phyrexian Altar by sacrificing the persist or undying creature, adding one mana of any color
- When the creature dies, its persist or undying ability triggers, returning it from your graveyard to the battlefield without a -1/-1 counter or a +1/+1 counter on it due to Solemnity
- Resolve the Phyrexian Altar ability
- Repeat
