Coveted Jewel, Kurkesh, Onakke Ancient, and Voltaic Key

Prerequisites

• Coveted Jewel on the battlefield
• Kurkesh, Onakke Ancient on the battlefield
• Voltaic Key on the battlefield

Steps

1. Activate Coveted Jewel by tapping it, adding
2. Activate Voltaic Key by paying and tapping it, targeting itself
3. Kurkesh triggers, causing you to pay to copy Voltaic Key's ability, targeting Coveted Jewel
4. Resolve both Voltaic Key abilities, untapping it and Coveted Jewel
5. Repeat

Results

• Infinite colored mana
• Infinite untap of artifacts you control