Idris, Soul of the TARDIS, Grim Monolith, and Zirda, the Dawnwaker

Prerequisites

• Idris, Soul of the TARDIS on the battlefield
• Grim Monolith in exile
• Zirda, the Dawnwaker on the battlefield
• Idris does not have summoning sickness

Steps

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

Results

• Infinite colorless mana