How can you create a combo with Prototype Portal, Clock of Omens, Grinding Station, Ancient Den?
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[START OF COMBO]This combo can be formed with Prototype Portal, Clock of Omens, Grinding Station, Ancient Den

Color identity: W
Mana cost: 
Steps:
  1. Activate Prototype Portal by paying {0} and tapping it, creating a token copy of Ancient Den.
  2. The Ancient Den token enters, triggering Grinding Station, untapping Grinding Station.
  3. Activate Clock of Omens by tapping the Ancient Den token and Grinding Station, untapping Prototype Portal.
  4. Repeat.[END OF COMBO STEPS]

Result:
  - Infinite landfall triggers
  - Infinite tapped land tokens[END OF COMBO RESULT][END OF COMBO]

Other prerequisites:
  - Prototype Portal must be on the battlefield
  - Clock of Omens must be on the battlefield
  - Grinding Station must be on the battlefield
  - Ancient Den must be exiled
[END OF COMBO PREREQUISITES]
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