How can you create a combo with Sedris, the Traitor King, Void Maw, Altar of Dementia, Witch Engine?
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[START OF COMBO]This combo can be formed with Sedris, the Traitor King, Void Maw, Altar of Dementia, Witch Engine

Color identity: UBR
Mana cost: {2}{B}
Steps:
  1. Activate Altar of Dementia by sacrificing Witch Engine, causing target player to mill cards equal to Witch Engine's power.
  2. Activate Witch Engine's unearth ability by paying {2}{B}, returning it from your graveyard to the battlefield, giving it haste and exiling it at end of turn or when it leaves the battlefield.
  3. Activate Witch Engine by tapping it.
  4. Holding priority, activate Altar of Dementia by sacrificing Witch Engine.
  5. Both Witch Engine's undying ability and Void Maw attempt to exile Witch Engine when it would be put into your graveyard.
  6. Choose to apply the Void Maw replacement effect, exiling Witch Engine.
  7. Resolve the Witch Engine ability from step 3, adding {B}{B}{B}{B}.
  8. Resolve the Altar of Dementia ability, causing target player to mill cards equal to Witch Engine's power.
  9. Activate Void Maw by putting Witch Engine from exile into your graveyard, giving Void Maw +2/+2 until end of turn.
  10. Repeat from step 2.[END OF COMBO STEPS]

Result:
  - Infinite black mana
  - Infinite enters the battlefield
  - Infinite leaves the battlefield
  - Infinitely large Void Maw until end of turn
  - Infinite mill
  - Infinite sacrifice triggers
  - Infinite self-mill[END OF COMBO RESULT][END OF COMBO]

Other prerequisites:
  - All permanants must be on the battlefield
[END OF COMBO PREREQUISITES]
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