Mortuary + Bile Urchin + Bolas's Citadel + Panicked Bystander // Cackling Culprit

Mortuary

Bile Urchin

Bolas's Citadel

Panicked Bystander // Cackling Culprit

How it works

1. Activate Bile Urchin by sacrificing it.
2. When Bile Urchin dies, Mortuary and Panicked Bystander // Cackling Culprit trigger.
3. Resolve the Mortuary trigger, putting Bile Urchin from your graveyard onto the top of your library.
4. Resolve the Panicked Bystander // Cackling Culprit trigger, causing you to gain 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 ingenious loop turns a modest one-mana sacrifice into a self-sustaining engine of life drain and death triggers. By letting you play cards directly from the top of your library while paying life instead of mana, Bolas's Citadel allows you to recast Bile Urchin repeatedly as it continuously recycles itself back to the library via Mortuary's placement trigger. Meanwhile, Panicked Bystander // Cackling Culprit acts as your crucial life buffer, offsetting the life paid to the Citadel with every creature death so you can safely keep the cycle going.