Metamorphosis Fanatic + Umbral Collar Zealot + Felidar Guardian

Metamorphosis Fanatic

Umbral Collar Zealot

Felidar Guardian

How it works

1. Cast Felidar Guardian by paying its mana cost.
2. When Felidar Guardian enters the battlefield, it triggers, targeting Metamorphosis Fanatic.
3. Holding priority, activate Umbral Collar Zealot by sacrificing Felidar Guardian.
4. Resolve the Felidar Guardian ability, blinking Metamorphosis Fanatic.
5. When Metamorphosis Fanatic enters the battlefield, it triggers, returning Felidar Guardian from your graveyard to the battlefield.
6. Repeat from step 2.

This clever loop relies on Felidar Guardian's entry trigger to blink Metamorphosis Fanatic, which in turn uses its own entry ability to fish Felidar Guardian right back out of your graveyard. Meanwhile, Umbral Collar Zealot acts as the sacrificial engine that sends Felidar Guardian back to the graveyard to start the cycle over, allowing you to filter your deck with infinite surveil triggers along the way. Because Metamorphosis Fanatic enters with lifelink and can instantly return your sacrificed pieces, you get an endless chain of entering and leaving the battlefield without ever running out of fuel.