Mortuary + Bolas's Citadel + Fanatical Firebrand + Popular Egotist

Mortuary

Bolas's Citadel

Fanatical Firebrand

Popular Egotist

How it works

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

This loop turns a humble goblin into a lethal engine by using Bolas's Citadel to cast spells directly from the top of your library for life instead of mana. When you activate Fanatical Firebrand to ping an opponent, Mortuary immediately catches it on its way to the graveyard and places it right back on top of your library where the Citadel can see it again. Meanwhile, Popular Egotist acts as the vital life-draining payoff, rewarding you with life and draining your opponent with every single sacrifice—easily offsetting the life you pay to recast the Firebrand over and over.