Basalt Monolith, Donatello, Mutant Mechanic, and Heartstone

Prerequisites

• Basalt Monolith on the battlefield
• Donatello, Mutant Mechanic on the battlefield
• Heartstone on the battlefield

Steps

1. Cause Basalt Monolith to become a creature using Donatello
2. Activate Basalt Monolith's first ability by tapping it, adding
3. Activate Basalt Monolith's last ability by paying , untapping it
4. Repeat from step 2

Results

• Infinite colorless mana