Doubling Cube, Voltaic Key, and Rings of Brighthearth

Prerequisites

• Doubling Cube on the battlefield
• Voltaic Key on the battlefield
• Rings of Brighthearth on the battlefield
• available

Steps

1. Float mana in your mana pool
2. Activate Doubling Cube by paying and tapping it, causing you to add
3. Activate Voltaic Key by paying and tapping it, targeting Doubling Cube
4. Rings of Brighthearth triggers, causing you to pay to copy Voltaic Key's ability, targeting Voltaic Key
5. Resolve both Voltaic Key abilities, untapping Voltaic Key and Doubling Cube
6. Repeat from step 2

Results

• Infinite mana artifacts you control can produce
• Infinite mana permanents you control can produce
• Infinite untap of artifacts you control