Rakdos, the Muscle + Priest of Gix + Haunted Crossroads + Umbral Collar Zealot + The Immortal Sun

Rakdos, the Muscle

Priest of Gix

Haunted Crossroads

Umbral Collar Zealot

The Immortal Sun

How it works

1. Activate Umbral Collar Zealot 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 Umbral Collar Zealot ability from step 1.
6. Cast Priest of Gix from exile by paying 2
7. When Priest of Gix enters the battlefield, it triggers, adding .
8. Repeat.

This loop spins into an infinite storm and execution engine by repeatedly cycling a single black mana source right back to the top of your library. You begin by using Umbral Collar Zealot to sacrifice Priest of Gix, generating the death trigger that lets Rakdos, the Muscle exile cards from the top of your library while also giving you a chance to stack your triggers. Before that exile resolves, you spend {B} via Haunted Crossroads to place the Priest right back on top of your library, ensuring it lands precisely where Rakdos's exile effect will catch it. Once you cast the Priest from exile for {2}, its entry triggers to refill your mana with {B}{B}{B}, comfortably paying for the entire loop with mana to spare thanks to The Immortal Sun reducing your spell costs.