Primal Prayers, Decoction Module, and Cavern Harpy

Prerequisites

• Primal Prayers on the battlefield
• Decoction Module on the battlefield
• Cavern Harpy in hand
• You have at least or enough mana to cast Cavern Harpy

Steps

1. Cast Cavern Harpy by paying due to Primal Prayers, if able, or by paying its mana cost
2. When Cavern Harpy enters the battlefield, it and Decoction Module trigger
3. Resolve the Decoction Module trigger, causing you to get
4. Resolve the Cavern Harpy trigger, returning it from the battlefield to your hand
5. Repeat

Results

• Infinite LTB
• Infinite ETB
• Infinite storm count