Mortuary + Moldervine Reclamation + Bile Urchin + Bolas's Citadel

Mortuary

Moldervine Reclamation

Bile Urchin

Bolas's Citadel

How it works

1. Activate Bile Urchin by sacrificing it.
2. When Bile Urchin dies, Mortuary and Moldervine Reclamation trigger.
3. Resolve the Moldervine Reclamation trigger, causing you to gain 1 life and draw a card.
4. Resolve the Mortuary trigger, putting Bile Urchin from your graveyard onto the top of your library.
5. Resolve the Bile Urchin ability.
6. Cast Bile Urchin from the top of your library by paying 1 life.
7. Repeat.

This wicked loop relies on Bolas's Citadel to let you cast creatures directly from the top of your library by paying life instead of mana. When you sacrifice Bile Urchin to drain your opponent, its death triggers Moldervine Reclamation to draw you that card while gaining back the life you spent, and Mortuary simultaneously places the urchin right back on top of your library. Because the Citadel lets you play it again immediately from the top, you can repeat this cycle endlessly to drain the table dry.