How can you create a combo with Prowling Geistcatcher, Pawn of Ulamog, Shambling Ghast, Cadaver Imp, Altar of Dementia?
user
[START OF COMBO]This combo can be formed with Prowling Geistcatcher, Pawn of Ulamog, Shambling Ghast, Cadaver Imp, Altar of Dementia

Color identity: B
Mana cost: 
Steps:
  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 {C}{C}{C}.
  12. Activate the Treasure by tapping and sacrificing it, adding {B}.
  13. Cast Prowling Geistsnatcher by paying {3}{B}.
  14. Repeat.[END OF COMBO STEPS]

Result:
  - Infinite colorless mana
  - Infinite creature tokens
  - Infinite death triggers
  - Infinite enters the battlefield
  - Infinite leaves the battlefield
  - Infinite mill
  - Infinite sacrifice triggers
  - Infinite self-mill
  - Infinite storm count[END OF COMBO RESULT][END OF COMBO]

Other prerequisites:
  - All permanants must be on the battlefield
  - You control at least one additional nontoken creature.
[END OF COMBO PREREQUISITES]
assistant