Rakdos, the Muscle + Priest of Gix + Haunted Crossroads + Ezzaroot Channeler + Yahenni, Undying Partisan

Rakdos, the Muscle

Priest of Gix

Haunted Crossroads

Ezzaroot Channeler

Yahenni, Undying Partisan

How it works

1. Activate Yahenni by sacrificing Priest of Gix.
2. When Priest of Gix dies, Rakdos triggers.
3. Holding priority, activate Haunted Crossroads by paying , putting Priest of Gix from your graveyard onto the top of your library.
4. Resolve the Rakdos trigger, causing you to exile the top three cards of your library with the ability to play them until your next end step.
5. Resolve the Yahenni ability from step 1.
6. Cast Priest of Gix from exile by paying at most 2.
7. When Priest of Gix enters the battlefield, it triggers, adding .
8. Repeat.

This intricate loop relies on Priest of Gix entering the battlefield to generate {B}{B}{B}, which easily pays for both the {B} activation of Haunted Crossroads to recycle the Priest back to the top of your library and the discounted cost to cast it from exile. Rakdos, the Muscle serves as the engine's primary enabler, exiling those top cards of your library whenever you sacrifice a creature so you can continually replay the Priest. Meanwhile, Yahenni, Undying Partisan acts as the necessary sacrifice outlet, while Ezzaroot Channeler's ability to reduce creature spell costs by the life you've gained ensures you always have enough mana left over to sustain the cycle indefinitely.