Basalt Monolith, Feldon of the Third Path, and Agatha of the Vile Cauldron

Prerequisites

• Basalt Monolith on the battlefield
• Feldon of the Third Path on the battlefield
• Agatha of the Vile Cauldron 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 at most , untapping it
4. Repeat from step 2

Results

• Infinite colorless mana