Rakdos, the Muscle + Shambling Ghast + Haunted Crossroads + Pitiless Plunderer + Yahenni, Undying Partisan

Rakdos, the Muscle

Shambling Ghast

Haunted Crossroads

Pitiless Plunderer

Yahenni, Undying Partisan

How it works

1. Activate Yahenni by sacrificing Shambling Ghast.
2. When Shambling Ghast dies, it, Pitiless Plunderer and Rakdos trigger.
3. Resolve the Shambling Ghast and Pitiless Plunderer triggers, creating two Treasure tokens.
4. Activate the Treasures by tapping and sacrificing them, adding 1.
5. Holding priority, activate Haunted Crossroads by paying , putting Shambling Ghast from your graveyard onto the top of your library.
6. Resolve the Rakdos trigger, exiling Shambling Ghast from the top of your library with the ability to cast it until your next turn.
7. Resolve the Yahenni ability.
8. Cast Shambling Ghast from exile by paying 1.
9. Repeat.

This loop relies on Rakdos, the Muscle acting as the engine that exiles Shambling Ghast off the top of your library whenever you feed it to Yahenni, Undying Partisan's sacrifice ability. Pitiless Plunderer and Shambling Ghast's own death trigger ensure you always generate the mana and treasures needed to recast the Ghast and activate Haunted Crossroads, which returns the creature back to the top of your library to keep the cycle going.