Idris, Soul of the TARDIS, Basalt Monolith, and Heartstone

Prerequisites

• Idris, Soul of the TARDIS on the battlefield
• Basalt Monolith in exile
• Heartstone on the battlefield

Steps

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

Results

• Infinite colorless mana