Rakdos, the Muscle + Priest of Gix + Haunted Crossroads + Umbral Collar Zealot + Skittering Precursor

Rakdos, the Muscle

Priest of Gix

Haunted Crossroads

Umbral Collar Zealot

Skittering Precursor

How it works

1. Activate Umbral Collar Zealot by sacrificing Priest of Gix.
2. When Priest of Gix dies, Skittering Precursor and Rakdos trigger.
3. Resolve the Skittering Precursor trigger, creating a creature token
4. Holding priority, activate Haunted Crossroads by paying , putting Priest of Gix from your graveyard onto the top of your library.
5. 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.
6. Resolve the Umbral Collar Zealot ability from step 1, putting a +1/+1 counter on it.
7. Activate the Eldrazi Spawn by sacrificing it, adding C.
8. Cast Priest of Gix from exile by paying 3.
9. When Priest of Gix enters the battlefield, it triggers, adding .
10. Repeat.

This loop uses Umbral Collar Zealot as the sacrifice outlet to feed Priest of Gix to the graveyard, where Haunted Crossroads can immediately cycle it back to the top of your library for a single black mana. Skittering Precursor keeps the engine churning by replacing every sacrificed nontoken with an Eldrazi Spawn token to help fund your spells, while Rakdos, the Muscle capitalizes on the carnage by exiling your library piece by piece so you can cast those cards from exile using any color of mana. Because Priest of Gix refunds three black mana upon entering the battlefield, the entire process becomes self-sustaining, letting you cycle through your deck infinitely and churn out boundless triggers.