Prosper, Tome-Bound + Ugin, the Ineffable + Eternal Scourge + Planar Void + Altar of Dementia

Prosper, Tome-Bound

Ugin, the Ineffable

Eternal Scourge

Planar Void

Altar of Dementia

How it works

1. Activate Altar of Dementia by sacrificing Eternal Scourge.
2. Planar Void triggers, exiling Eternal Scourge from your graveyard.
3. Resolve the Altar of Dementia ability, milling target player for an amount equal to Eternal Scourge's power.
4. Cast Eternal Scourge for 1.
5. Prosper triggers, creating a Treasure token.
6. Resolve Eternal Scourge, allowing it to enter the battlefield.
7. Activate the Treasure token by tapping and sacrificing it, adding one mana of any color.
8. Repeat.