Mortuary + Falkenrath Noble + Bolas's Citadel + Goblin Firestarter

Mortuary

Falkenrath Noble

Bolas's Citadel

Goblin Firestarter

How it works

1. Activate Goblin Firestarter by sacrificing it.
2. When Goblin Firestarter dies, Mortuary and Falkenrath Noble trigger.
3. Resolve the Mortuary trigger, putting Goblin Firestarter from your graveyard onto the top of your library.
4. Resolve the Falkenrath Noble 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 turns a humble Goblin Firestarter into a lethal self-sustaining engine by letting you replay it directly from the top of your library for life instead of mana, thanks to the alternative payment system granted by Bolas's Citadel. Every time you sacrifice the Goblin, Mortuary immediately intercepts it in the graveyard to place it right back on top of your library, while Falkenrath Noble drains your opponents' life totals and pads your own life total to offset the cost of casting it again. It's a remarkably efficient loop in formats like Commander and Legacy where you can easily churn through your entire deck, convert those triggers into a mountain of damage, and leave your foes in the dust.