Mortuary + Bolas's Citadel + Fear of Lost Teeth + Phantom Train

Mortuary

Bolas's Citadel

Fear of Lost Teeth

Phantom Train

How it works

1. Activate Phantom Train 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 Phantom Train 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 loop creates a brilliantly morbid self-sustaining engine, turning a humble train into a lethal conveyance fueled by the afterlife. By using Phantom Train to sacrifice Fear of Lost Teeth, you trigger its death ability while Mortuary steps in to immediately recycle the creature straight to the top of your library. From there, Bolas's Citadel allows you to bypass mana costs entirely, letting you recast Fear of Lost Teeth over and over by simply paying its mana value as life—a cost easily offset by the life you gain from the fear itself.