Basalt Monolith, Feldon of the Third Path, and Heartstone

Prerequisites

• Basalt Monolith on the battlefield
• Feldon of the Third Path on the battlefield
• Heartstone on the battlefield
• available

Steps

1. Cause Basalt Monolith to become a creature using Feldon of the Third Path
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