Umbral Collar Zealot + Fiend Hunter + Metamorphosis Fanatic

Umbral Collar Zealot

Fiend Hunter

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 Umbral Collar Zealot 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 Umbral Collar Zealot ability.
8. Repeat from step 3.

This clever loop transforms an ordinary sacrifice outlet into a perpetual motion machine by exploiting the interaction between Fiend Hunter and Metamorphosis Fanatic. When Fiend Hunter enters the battlefield to exile Metamorphosis Fanatic, you can use Umbral Collar Zealot to sacrifice the Hunter, sending it to the graveyard and freeing the Fanatic. The returning Metamorphosis Fanatic immediately triggers to pull Fiend Hunter right back out of the graveyard and onto the battlefield, restarting the cycle. Because Umbral Collar Zealot's ability requires you to sacrifice a creature or artifact as a cost, sacrificing Fiend Hunter along the way lets you repeatedly surveil your entire library while generating infinite enters-the-battlefield, leaves-the-battlefield, and death triggers.