Golgari Thug + Shilgengar, Sire of Famine + Bolas's Citadel + Vein Ripper

Golgari Thug

Shilgengar, Sire of Famine

Bolas's Citadel

Vein Ripper

How it works

1. Activate Shilgengar by sacrificing Golgari Thug.
2. When Golgari Thug dies, it and Vein Ripper trigger.
3. Resolve the Golgari Thug trigger, putting it from your graveyard onto the top of your library.
4. Resolve the Vein Ripper trigger, causing you to gain 2 life and target opponent to lose 2 life.
5. Resolve the Shilgengar ability.
6. Cast Golgari Thug from the top of your library by paying 2 life.
7. Repeat.

This intricate engine harnesses Shilgengar, Sire of Famine as the sacrifice outlet that feeds Blood tokens into its own massive recursion ability, while Bolas's Citadel allows you to continuously cast spells straight from the top of your library by paying life instead of mana. Golgari Thug is the fuel that keeps this loop turning, since its own death trigger puts it right back onto the top of your library for the Citadel to play again, which in turn offsets the life payment through Vein Ripper draining your opponents and gaining you life every time a creature dies.