Spawning Pit + Faceless Butcher + Metamorphosis Fanatic

Spawning Pit

Faceless Butcher

Metamorphosis Fanatic

How it works

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