Fiend Hunter + Yahenni, Undying Partisan + Metamorphosis Fanatic

Fiend Hunter

Yahenni, Undying Partisan

Metamorphosis Fanatic

How it works

1. Cast Fiend Hunter by paying its mana cost.
2. When Fiend Hunter enters, its first ability triggers, exiling Metamorphosis Fanatic.
3. Activate Yahenni by sacrificing Fiend Hunter.
4. When Fiend Hunter dies, its second ability triggers, returning Metamorphosis Fanatic from exile to the battlefield.
5. When Metamorphosis Fanatic enters, it triggers, returning Fiend Hunter from your graveyard to the battlefield.
6. When Fiend Hunter enters, its first ability triggers, exiling Metamorphosis Fanatic.
7. Resolve the Yahenni ability.
8. Repeat from step 3.

This elegant loop sets up a perpetual recursion engine centered around a self-sustaining exchange between Fiend Hunter and Metamorphosis Fanatic. By utilizing Yahenni, Undying Partisan's sacrifice ability to intentionally trigger Fiend Hunter's leaving-the-battlefield effect, you can immediately pull Metamorphosis Fanatic back from exile. In turn, Metamorphosis Fanatic's entry ability fishes Fiend Hunter straight out of the graveyard to start the cycle anew, letting you reap endless sacrifice and trigger benefits at will.