Mortuary + Bolas's Citadel + Phyrexian Dreadnought + Grave Venerations

Mortuary

Bolas's Citadel

Phyrexian Dreadnought

Grave Venerations

How it works

1. Cast Phyrexian Dreadnought from the top of your library by paying 1 life.
2. When Phyrexian Dreadnought enters, it triggers, causing you to sacrifice it.
3. When Phyrexian Dreadnought dies, Mortuary and Grave Venerations trigger.
4. Resolve the Mortuary trigger, putting Phyrexian Dreadnought from your graveyard onto the top of your library.
5. Resolve the Grave Venerations trigger, causing you to gain 1 life and each opponent to lose 1 life.
6. Repeat.

This elegant loop turns the top of your library into an endless engine of life and death, all anchored by Bolas's Citadel allowing you to cast spells directly from your library by paying life instead of mana. By playing Phyrexian Dreadnought for a mere 1 life, you immediately trigger its sacrifice clause upon entry, sending it straight to the graveyard. There, Mortuary intercepts the creature and instantly places it back onto the top of your library to be recast, while Grave Venerations turns every single iteration of this cycle into a drain on your opponents' life totals and a replenishment of your own.