How can you create a combo with Riku of Two Reflections, Narset's Reversal, Twice Upon a Time // Unlikely Meeting?
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[START OF COMBO]This combo can be formed with Riku of Two Reflections, Narset's Reversal, Twice Upon a Time // Unlikely Meeting

Color identity: GUR
Mana cost: {4}{U}{U}{U}{U}{U}{R} each turn
Steps:
  1. Cast Twice Upon a Time by paying {4}{U}{U}.
  2. Riku's first ability triggers - choose not to pay.
  3. Holding priority, cast Narset's Reversal by paying {U}{U}, targeting Twice Upon a Time.
  4. Riku's first ability triggers, causing you to pay {U}{R} to copy Narset's Reversal, with the copy targeting the original Narset's Reversal.
  5. Resolve the copy of Narset's Reversal, copying the original Narset's Reversal targeting Twice Upon a Time, and returning the original Narset's Reversal to your hand.
  6. Resolve the copy of Narset's Reversal created in step 5, copying Twice Upon a Time and returning the original Twice Upon a Time to your hand.
  7. Resolve Twice Upon a Time, causing you to take an extra turn after this one.
  8. Repeat each turn.[END OF COMBO STEPS]

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

Other prerequisites:
  - Riku of Two Reflections must be on the battlefield
  - Narset's Reversal must be in your hand
  - Twice Upon a Time // Unlikely Meeting must be in your hand
  - You control at least two Doctors.
[END OF COMBO PREREQUISITES]
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