How can you create a combo with Hidetsugu, Devouring Chaos, Intruder Alarm, Mortuary, Stonecoil Serpent?
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[START OF COMBO]This combo can be formed with Hidetsugu, Devouring Chaos, Intruder Alarm, Mortuary, Stonecoil Serpent

Color identity: UBR
Mana cost: 
Steps:
  1. Activate all mana-producing creatures you control by tapping them, adding at least {3}{R}.
  2. Cast Stonecoil Serpent by paying {0}.
  3. Stonecoil Serpent enters the battlefield and dies as a state-based action due to having zero toughness.
  4. Intruder Alarm and Mortuary trigger.
  5. Resolve the Intruder Alarm trigger, untapping all creatures.
  6. Resolve the Mortuary trigger, putting Stonecoil Serpent on top of your library from your graveyard.
  7. Activate Hidetsugu's second ability by paying {2}{R} and tapping it, exiling Stonecoil Serpent from the top of your library and allowing you cast it this turn.
  8. Repeat.[END OF COMBO STEPS]

Result:
  - Infinite +1/+1 counters on Stonecoil Serpent
  - Infinite death triggers
  - Infinite enters the battlefield
  - Infinite leaves the battlefield
  - Infinite mana creatures you control can produce
  - Infinite storm count
  - Infinite untap of all creatures[END OF COMBO RESULT][END OF COMBO]

Other prerequisites:
  - Hidetsugu, Devouring Chaos must be on the battlefield
  - Intruder Alarm must be on the battlefield
  - Mortuary must be on the battlefield
  - Stonecoil Serpent must be in your hand
  - Hidetsugu does not have summoning sickness.
  - Creatures you control can tap to produce at least {3}{R}.
[END OF COMBO PREREQUISITES]
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