Mortuary + Crimson Kobolds + Bolas's Citadel + Carrion Feeder

Mortuary

Crimson Kobolds

Bolas's Citadel

Carrion Feeder

How it works

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

This clever loop uses Mortuary as a tireless conveyor belt, ensuring that any creature you send to the graveyard goes straight back to the top of your library instead. With Bolas's Citadel granting you the power to cast spells directly from the top of your library for life instead of mana, and Crimson Kobolds carrying a mana value of zero, you can recast them for free endlessly. Carrion Feeder acts as the engine's hungry sacrifice outlet, growing stronger with infinite +1/+1 counters while repeatedly triggering death and leave-the-battlefield effects at zero resource cost.