Karn, Silver Golem, Freed from the Real, and Doubling Cube

Prerequisites

• Karn, Silver Golem on the battlefield
• Freed from the Real in hand
• Doubling Cube on the battlefield
• available

Steps

1. Activate Doubling Cube by paying and tapping it, doubling your unspent mana
2. Activate Karn by paying , causing Doubling Cube to become an artifact creature until end of turn
3. Cast Freed from the Real by paying , enchanting Doubling Cube
4. Activate Freed from the Real's second ability by paying , untapping Doubling Cube
5. Activate Doubling Cube by paying and tapping it, doubling your unspent mana
6. Repeat from step 4

Results

• Infinite colored mana
• Infinite colorless mana