Birgi, God of Storytelling // Harnfel, Horn of Bounty, Dualcaster Mage, and Snap

Prerequisites

• Birgi, God of Storytelling // Harnfel, Horn of Bounty on the battlefield
• Dualcaster Mage in hand
• Snap in hand
• available

Steps

1. Cast Snap
2. Birgi triggers, adding
3. Holding priority, cast Dualcaster Mage
4. Birgi triggers, adding
5. Dualcaster Mage enters the battlefield, copying Snap, with the copy targeting Dualcaster Mage
6. Resolve the copy of Snap, returning Dualcaster Mage to your hand and untapping the two lands
7. Holding priority, tap those 2 lands for
8. Repeat steps 3-7

Results

• Infinite ETB
• Infinite LTB
• Infinite storm count
• Infinite magecraft triggers
• Infinite mana lands you control can produce
• Infinite untap of lands you control