Basalt Monolith, Living Brain, Mechanical Marvel, and Agatha of the Vile Cauldron

Prerequisites

• Basalt Monolith on the battlefield
• Living Brain, Mechanical Marvel on the battlefield
• Agatha of the Vile Cauldron on the battlefield

Steps

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

Results

• Infinite colorless mana