Voltaic Key, Empowered Autogenerator, and Rings of Brighthearth

Prerequisites

• Voltaic Key on the battlefield
• Empowered Autogenerator on the battlefield
• Rings of Brighthearth on the battlefield
• Empowered Autogenerator has at least two charge counters on it

Steps

1. Activate Empowered Autogenerator by tapping it, putting a charge counter on it and adding one mana of any color for each charge counter on Empowered Autogenerator
2. Activate Voltaic Key by paying and tapping it, targeting Empowered Autogenerator
3. Rings of Brighthearth triggers, costing you to copy Voltaic Key's ability, targeting Voltaic Key
4. Resolve both Voltaic Key abilities, untapping Voltaic Key and Empowered Autogenerator
5. Repeat

Results

• Infinite charge counters on Empowered Autogenerator
• Infinite colored mana
• Infinite mana artifacts you control can produce
• Infinite untap of artifacts you control