Voltaic Construct, Coveted Jewel, and Xenic Poltergeist

Prerequisites

• Voltaic Construct on the battlefield
• Coveted Jewel on the battlefield
• Xenic Poltergeist on the battlefield
• Xenic Poltergeist does not have summoning sickness
• Coveted Jewel does not have summoning sickness

Steps

1. Activate Xenic Poltergeist by tapping it, causing Coveted Jewel to become an artifact creature until your next upkeep
2. Activate Coveted Jewel by tapping it, adding three mana of any one color
3. Activate Voltaic Construct by paying , untapping Coveted Jewel
4. Repeat from step 2

Results

• Infinite colored mana