Mortuary + Bile Urchin + Bolas's Citadel + Sephiroth, Fabled SOLDIER // Sephiroth, One-Winged Angel

Mortuary

Bile Urchin

Bolas's Citadel

Sephiroth, Fabled SOLDIER // Sephiroth, One-Winged Angel

How it works

1. Activate Bile Urchin by sacrificing it.
2. When Bile Urchin dies, Mortuary and Sephiroth, Fabled SOLDIER // Sephiroth, One-Winged Angel trigger.
3. Resolve the Mortuary trigger, putting Bile Urchin from your graveyard onto the top of your library.
4. Resolve the Sephiroth, Fabled SOLDIER // Sephiroth, One-Winged Angel trigger, causing you to gain 1 life and target opponent to lose 1 life.
5. Resolve the Bile Urchin ability.
6. Cast Bile Urchin from the top of your library by paying 1 life.
7. Repeat.

This loop turns a humble little 1-mana artifact creature into a lethal loop by using Bolas's Citadel to cast spells straight from the top of your library for life instead of mana. Whenever you sacrifice Bile Urchin to drain an opponent, Mortuary immediately intercepts it from your graveyard and places it right back on top of your library to keep the chain going. Meanwhile, Sephiroth, Fabled SOLDIER // Sephiroth, One-Winged Angel watches every single creature die, turning each loop into an extra life drain and lifegain trigger that easily offsets the life you pay to recast the urchin.