Mortuary + Vindictive Vampire + Bolas's Citadel + Goblin Firestarter

Mortuary

Vindictive Vampire

Bolas's Citadel

Goblin Firestarter

How it works

1. Activate Goblin Firestarter by sacrificing it.
2. When Goblin Firestarter dies, Mortuary and Vindictive Vampire trigger.
3. Resolve the Mortuary trigger, putting Goblin Firestarter from your graveyard onto the top of your library.
4. Resolve the Vindictive Vampire trigger, causing you to gain 1 life and dealing 1 damage to each opponent.
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 an engine of endless doom by leveraging the top-of-library manipulation provided by Mortuary. With Bolas's Citadel allowing you to cast the goblin straight from the top of your library using life instead of mana, you can infinitely recast and sacrifice it without ever spending a single land. Meanwhile, Vindictive Vampire quietly watches the carnage, draining your opponents' life totals and padding your own life total with every single repetition to safely fuel the Citadel's cost.