Mortuary + Bolas's Citadel + Bontu's Monument + Phantom Train

Mortuary

Bolas's Citadel

Bontu's Monument

Phantom Train

How it works

1. Activate Phantom Train by sacrificing a creature with mana value 1 or less.
2. When the creature dies, Mortuary triggers, putting the creature from your graveyard onto the top of your library.
3. Resolve the Phantom Train ability.
4. Cast the creature from the top of your library by paying 1 life.
5. Bontu's Monument triggers, causing you to gain 1 life and each opponent to lose 1 life.
6. Repeat.

This engine transforms a modest loop into a relentless storm by leveraging the top-deck manipulation of Mortuary alongside the alternative casting engine of Bolas's Citadel. Since Bolas's Citadel lets you cast that creature straight off the top by paying life instead of mana, you can continually feed the sacrifice cost of Phantom Train without ever running out of fodder. Meanwhile, Bontu's Monument cushions the life cost of the Citadel while draining your opponents to zero, turning a perpetual cycle of sacrifice and rebirth into an unyielding torrent of death and lifegain triggers.