Idris, Soul of the TARDIS, Grim Monolith, and Agatha of the Vile Cauldron

Prerequisites

• Idris, Soul of the TARDIS on the battlefield
• Grim Monolith in exile
• Agatha of the Vile Cauldron on the battlefield
• Idris does not have summoning sickness
• Agatha of the Vile Cauldron has power 2 or greater

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 at most , untapping it
3. Repeat

Results

• Infinite colorless mana