Prowling Geistcatcher + Pawn of Ulamog + Shambling Ghast + Cadaver Imp + Altar of Dementia

Prowling Geistcatcher

Pawn of Ulamog

Shambling Ghast

Cadaver Imp

Altar of Dementia

How it works

1. Activate Altar of Dementia four times by sacrificing Cadaver Imp, Shambling Ghast, Pawn of Ulamog and another nontoken creature.
2. Pawn of Ulamog and Prowling Geistsnatcher trigger four times each, and Shambling Ghast triggers once.
3. Resolve the Shambling Ghast trigger, creating a Treasure token.
4. Resolve all Pawn of Ulamog triggers, creating four 0/1 Eldrazi Spawn creature tokens.
5. Resolve all Prowling Geistsnatcher triggers, exiling the sacrificed creatures.
6. Resolve all Altar of Dementia abilities, causing target player to mill cards equal to the sacrificed creatures' powers.
7. Activate Altar of Dementia by sacrificing Prowling Geistsnatcher.
8. Prowling Geistsnatcher leaves the battlefield, returning all cards exiled with it to the battlefield.
9. Cadaver Imp enters the battlefield, returning Prowling Geistsnatcher from your graveyard to your hand.
10. Resolve the Altar of Dementia ability from step 7, causing target player to mill cards equal to Prowling Geistsnatcher's power.
11. Activate three Eldrazi Spawn tokens by sacrificing them, adding CCC.
12. Activate the Treasure by tapping and sacrificing it, adding .
13. Cast Prowling Geistsnatcher by paying 3.
14. Repeat.