Thermopod + Heartmender + Thran Vigil

Thermopod

Heartmender

Thran Vigil

How it works

1. Activate Thermopod 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 engine transforms a simple sacrifice loop into a fountain of infinite red mana and endless triggers by leveraging the interaction between counters and the graveyard. When you feed Heartmender to Thermopod, its persist ability brings it back bearing a -1/+1 counter instead of sticking around in the graveyard, which simultaneously satisfies Thran Vigil to immediately neutralize that drawback with a +1/+1 counter. Because Heartmender naturally clears away any lingering -1/-1 counters at the start of your turn, the loop remains completely self-sustaining whenever you need to pop off.