Mortuary + Bile Urchin + Bolas's Citadel + Vengeful Bloodwitch

Mortuary

Bile Urchin

Bolas's Citadel

Vengeful Bloodwitch

How it works

1. Activate Bile Urchin by sacrificing it.
2. When Bile Urchin dies, Mortuary and Vengeful Bloodwitch trigger.
3. Resolve the Mortuary trigger, putting Bile Urchin from your graveyard onto the top of your library.
4. Resolve the Vengeful Bloodwitch 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 delightfully morbid loop transforms the simple, persistent casting of Bile Urchin into a relentless engine of doom. With Bolas's Citadel providing the crucial ability to cast spells directly from the top of your library by paying life instead of mana, you can repeatedly redeploy the Urchin the moment Mortuary tucks it safely back onto your library. Meanwhile, Vengeful Bloodwitch watches the continuous procession of sacrifices, turning every single death into an escalating drain of life that rapidly overwhelms your opponents.