How can you create a combo with Heartstone, Basalt Monolith, Karn's Touch?
user
[START OF COMBO]This combo can be formed with Heartstone, Basalt Monolith, Karn's Touch

Color identity: U
Mana cost: {U}{U}
Steps:
  1. Cast Karn's Touch by paying {U}{U}, targeting Basalt Monolith.
  2. Activate Basalt Monolith's first ability by tapping it, adding {C}{C}{C}.
  3. Activate Basalt's Monolith's last ability by paying {2}, untapping it.
  4. Repeat.[END OF COMBO STEPS]

Result:
  - Infinite colorless mana[END OF COMBO RESULT][END OF COMBO]

Other prerequisites:
  - Heartstone must be on the battlefield
  - Basalt Monolith must be on the battlefield
  - Karn's Touch must be in your hand
  - Basalt Monolith does not have summoning sickness.
[END OF COMBO PREREQUISITES]
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