How can you create a combo with Mnemonic Wall, Erratic Portal, Capture of Jingzhou?
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[START OF COMBO]This combo can be formed with Mnemonic Wall, Erratic Portal, Capture of Jingzhou

Color identity: U
Mana cost: {6}{U}{U}{U}{U} each turn
Steps:
  1. Cast Capture of Jingzhou by paying {3}{U}{U}, taking an extra turn after this one.
  2. Cast Mnemonic Wall by paying {4}{U}.
  3. Mnemonic Wall enters the battlefield, returning Capture of Jingzhou from your graveyard to your hand.
  4. Activate Erratic Portal by paying {1} and tapping it, returning Mnemonic Wall from the battlefield to your hand.
  5. Repeat each turn.[END OF COMBO STEPS]

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

Other prerequisites:
  - Mnemonic Wall must be in your hand
  - Erratic Portal must be on the battlefield
  - Capture of Jingzhou must be in your hand
[END OF COMBO PREREQUISITES]
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