Mortuary + Bolas's Citadel + Goblin Firestarter + Susurian Voidborn

Mortuary

Bolas's Citadel

Goblin Firestarter

Susurian Voidborn

How it works

1. Activate Goblin Firestarter by sacrificing it.
2. When Goblin Firestarter dies, Mortuary and Susurian Voidborn trigger.
3. Resolve the Mortuary trigger, putting Goblin Firestarter from your graveyard onto the top of your library.
4. Resolve the Susurian Voidborn trigger, causing you to gain 1 life and target opponent to lose 1 life.
5. Resolve the Goblin Firestarter ability.
6. Cast Goblin Firestarter from the top of your library by paying 1 life.
7. Repeat.

This loop transforms the humble Goblin Firestarter into an endless engine of attrition by using Mortuary to instantly recycle the goblin back to the top of your library every time it bites the dust. Bolas's Citadel makes casting the goblin from the top seamless, letting you pay life instead of mana to keep the cycle spinning infinitely. Meanwhile, Susurian Voidborn watches over the carnage, turning every single sacrifice into a life-draining drain-and-gain loop that finishes off your opponents once and for all.