Voltaic Construct, Karn, the Great Creator, and Dreamstone Hedron

Prerequisites

• Voltaic Construct on the battlefield
• Karn, the Great Creator on the battlefield
• Dreamstone Hedron on the battlefield

Steps

1. Animate Dreamstone Hedron using Karn, the Great Creator
2. Activate Dreamstone Hedron by tapping it, adding
3. Activate Voltaic Construct by paying , untapping Dreamstone Hedron
4. Repeat from step 2

Results

• Infinite colorless mana
• Infinite untap of artifact creatures you control