Mortuary + Carrion Feeder + Ornithopter + Gwenom, Remorseless

Mortuary

Carrion Feeder

Ornithopter

Gwenom, Remorseless

How it works

1. Activate Carrion Feeder by sacrificing Ornithopter
2. When Ornithopter dies, Mortuary triggers, putting Ornithopter from your graveyard onto the top of your library.
3. Resolve the Carrion Feeder ability.
4. Cast Ornithopter from the top of your library by paying 0 life.
5. Repeat.

This loop uses Carrion Feeder to repeatedly sacrifice the zero-mana Ornithopter, pumping Carrion Feeder larger with every iteration while triggering endless deaths and enters-the-battlefield events. Normally, sacrificing a creature sends it to the graveyard, but Mortuary intercepts this by immediately placing Ornithopter back on top of your library whenever it leaves the battlefield. To complete the circuit, Gwenom, Remorseless allows you to play that top-decked Ornithopter for its alternative life-payment cost—which, in the case of a zero-mana artifact, costs you zero life.