Sister Hospitaller + Fiend Hunter + Yahenni, Undying Partisan

Sister Hospitaller

Fiend Hunter

Yahenni, Undying Partisan

How it works

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

This loop transforms a modest sacrifice engine into an infinite recursion machine by exploiting the precise timing of enter-the-battlefield and leave-the-battlefield triggers. With Yahenni, Undying Partisan standing ready to consume your creatures for protection, you sacrifice Fiend Hunter to trigger its departure, which in turn releases Sister Hospitaller from exile. The moment Sister Hospitaller re-enters the battlefield, her ability immediately plucks Fiend Hunter right back out of your graveyard, restarting the cycle and gaining you life based on the hunter's mana value along the way.