Sister Hospitaller + Phyrexian Altar + Fiend Hunter

Sister Hospitaller

Phyrexian Altar

Fiend Hunter

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 Phyrexian Altar 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. Repeat from step 3.

This elegant loop sets up a continuous cycle of life and sacrifice by leveraging recursive triggers between the graveyard and the battlefield. Once Fiend Hunter enters the fray to exile Sister Hospitaller, you can instantly feed Fiend Hunter to Phyrexian Altar to trigger its departure. That death triggers Sister Hospitaller's return from exile, and when Sister Hospitaller enters, its own ability plucks Fiend Hunter right back out of the graveyard to restart the whole chain.