Stalwart Successor + Ashnod's Altar + Lingering Tormentor

Stalwart Successor

Ashnod's Altar

Lingering Tormentor

How it works

1. Activate Ashnod's Altar by sacrificing Lingering Tormentor
2. When Lingering Tormentor dies, its persist ability triggers, returning it from your graveyard to the battlefield with a -1/-1 counter on it.
3. When Lingering Tormentor enters, Stalwart Successor triggers, putting a +1/+1 counter on Lingering Tormentor
4. Repeat.

This clever loop turns Ashnod's Altar into an engine for infinite mana, death triggers, and enter-the-battlefield effects by exploiting the fragile state of Lingering Tormentor. When you sacrifice Lingering Tormentor to the Altar, its persist ability brings it back to the battlefield with a -1/-1 counter, but the crucial presence of Stalwart Successor immediately triggers to place a +1/+1 counter on it as the first counters put on the creature that turn. Because state-based actions instantly cause the +1/+1 counter and the -1/-1 counter to annihilate each other, Lingering Tormentor is left completely clean of counters and ready to be sacrificed all over again.