Golgari Thug + Umbral Collar Zealot + Dross Harvester + Bolas's Citadel

Golgari Thug

Umbral Collar Zealot

Dross Harvester

Bolas's Citadel

How it works

1. Activate Umbral Collar Zealot by sacrificing Golgari Thug.
2. When Golgari Thug dies, it and Dross Harvester trigger.
3. Resolve the Golgari Thug trigger, putting it from your graveyard onto the top of your library.
4. Resolve the Dross Harvester trigger, causing you to gain 2 life.
5. Resolve the Umbral Collar Zealot ability.
6. Cast Golgari Thug from the top of your library by paying 2 life.
7. Repeat.

This intricate loop is masterminded by Bolas's Citadel, which lets you cast spells straight from the top of your library by paying life rather than mana. You use Umbral Collar Zealot as a sacrifice outlet to feed the loop, sending Golgari Thug to the graveyard where its death trigger places it right back on top of your library. Meanwhile, Dross Harvester steps in to pad your life total whenever a creature dies, offsetting the life you spent casting the Thug over and over again.