Basalt Monolith, Bello, Bard of the Brambles, and Heartstone

Prerequisites

• Basalt Monolith on the battlefield
• Bello, Bard of the Brambles on the battlefield
• Heartstone on the battlefield
• It is your turn

Steps

1. Activate Basalt Monolith's first ability by tapping it, adding
2. Activate Basalt Monolith's last ability by paying , untapping it
3. Repeat

Results

• Infinite colorless mana