Ensoul Artifact, Grim Monolith, and Training Grounds

Prerequisites

• Ensoul Artifact on the battlefield
• Grim Monolith on the battlefield
• Training Grounds on the battlefield

Steps

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

Results

• Infinite colorless mana