Phyrexian Altar + Heartmender + Thran Vigil

Phyrexian Altar

Heartmender

Thran Vigil

How it works

1. Activate Phyrexian Altar by sacrificing Heartmender.
2. When Heartmender dies, its persist ability triggers, returning it from your graveyard to the battlefield with a -1/-1 counter on it.
3. Thran Vigil triggers, putting a +1/+1 counter on Heartmender.
4. Repeat.

This clever loop turns Heartmender into a self-sustaining engine by exploiting the interaction between persist and its own upkeep ability. When you sacrifice Heartmender to Phyrexian Altar, its persist ability normally brings it back with a detrimental -1/-1 counter; however, Thran Vigil triggers when Heartmender leaves your graveyard, placing a +1/+1 counter that immediately annihilates that -1/-1 counter via state-based actions. This leaves Heartmender permanently cleansed and ready to be sacrificed again, letting Phyrexian Altar endlessly recycle the creature for an infinite supply of colored mana, death triggers, and sacrifice triggers.