Voltaic Key, Forsaken Monument, Rings of Brighthearth, and Dreamstone Hedron

Prerequisites

• Voltaic Key on the battlefield
• Forsaken Monument on the battlefield
• Rings of Brighthearth on the battlefield
• Dreamstone Hedron on the battlefield

Steps

1. Activate Dreamstone Hedron by tapping it, adding
2. Forsaken Monument triggers, adding
3. Activate Voltaic Key by paying and tapping it, targeting itself
4. Rings of Brighthearth triggers, causing you to pay to copy Voltaic Key's ability, targeting Dreamstone Hedron
5. Resolve both Voltaic Key abilities, untapping it and Dreamstone Hedron
6. Repeat

Results

• Infinite untap of all artifacts you control