How can you create a combo with The Sixth Doctor, Karn's Temporal Sundering, Isochron Scepter, Unsubstantiate?
user
[START OF COMBO]This combo can be formed with The Sixth Doctor, Karn's Temporal Sundering, Isochron Scepter, Unsubstantiate

Color identity: GU
Mana cost: {6}{U}{U} each turn
Steps:
  1. Cast Karn's Temporal Sundering by paying {4}{U}{U}.
  2. The Sixth Doctor triggers, copying Karn's Temporal Sundering.
  3. Resolve the copy of Karn's Temporal Sundering, causing you to take an extra turn after this one.
  4. Holding priority, activate Isochron Scepter by paying {2} and tapping it, casting a copy of Unsubstantiate without paying its mana cost.
  5. Resolve Unsubstantiate, returning the original Karn's Temporal Sundering to your hand.
  6. Repeat each turn.[END OF COMBO STEPS]

Result:
  - Infinite turns[END OF COMBO RESULT][END OF COMBO]

Other prerequisites:
  - The Sixth Doctor must be on the battlefield
  - Karn's Temporal Sundering must be in your hand
  - Isochron Scepter must be on the battlefield
  - Unsubstantiate must be exiled
[END OF COMBO PREREQUISITES]
assistant