Mortuary + Woe Strider + Bolas's Citadel + Willow Geist

Mortuary

Woe Strider

Bolas's Citadel

Willow Geist

How it works

1. Activate Woe Strider by sacrificing Willow Geist.
2. When Willow Geist dies, it and Mortuary triggers.
3. Resolve the Mortuary trigger, putting Willow Geist from your graveyard onto the top of your library.
4. Resolve the Willow Geist trigger, causing you to gain 1 life
5. Resolve the Woe Strider ability.
6. Cast Willow Geist from the top of your library by paying 1 life due to Bolas's Citadel.
7. Repeat.

This engine creates a seamless loop by turning the top of your library into an extension of your hand using Bolas's Citadel, allowing you to cast spells by paying life instead of mana. When you sacrifice Willow Geist to Woe Strider, Mortuary immediately intercepts the creature as it hits the graveyard, neatly tucking it back onto the very top of your library just in time for the Citadel to play it again. Meanwhile, Woe Strider's sacrifice outlet keeps the loop moving while letting you scry away unwanted draws, and Willow Geist quietly triggers its own death ability to offset the life payment required by the Citadel.