Mortuary + Umbral Collar Zealot + Bolas's Citadel + Fear of Lost Teeth

Mortuary

Umbral Collar Zealot

Bolas's Citadel

Fear of Lost Teeth

How it works

1. Activate Umbral Collar Zealot by sacrificing Fear of Lost Teeth.
2. When Fear of Lost Teeth dies, it and Mortuary triggers.
3. Resolve the Mortuary trigger, putting Fear of Lost Teeth from your graveyard onto the top of your library.
4. Resolve the Fear of Lost Teeth trigger, causing you to gain 1 life and dealing 1 damage to any target.
5. Resolve the Umbral Collar Zealot ability.
6. Cast Fear of Lost Teeth from the top of your library by paying 1 life due to Bolas's Citadel.
7. Repeat.

This intricate loop lets you leverage Bolas's Citadel to continually cast spells straight from the top of your library by paying life rather than mana costs. The engine relies on Umbral Collar Zealot as your sacrifice outlet, which feeds Fear of Lost Teeth into the graveyard so it can trigger its own death ability. As Fear of Lost Teeth hits the graveyard, Mortuary intercepts the card and places it right back onto the top of your library, perfectly positioned for the Citadel's alternate casting cost. Each iteration costs just a single point of life while netting you life back and dealing unyielding damage, easily clearing the board or draining your opponents out of the game.