Underworld Breach, Grinding Station, and Mox Opal

Prerequisites

• Underworld Breach on the battlefield
• Grinding Station on the battlefield
• Mox Opal on the battlefield

Steps

1. If you control three or more artifacts, activate Mox Opal by tapping it, adding one mana of any color
2. Activate Grinding Station by tapping it and sacrificing Mox Opal, causing yourself to mill three cards
3. Cast Mox Opal from your graveyard for its escape cost by exiling three cards from your graveyard
4. When Mox Opal enters the battlefield, Grinding Station triggers, untapping Grinding Station
5. Repeat

Results

• Infinite self-mill
• Near-infinite storm count
• Near-infinite colored mana