Beastcaller Savant, Cloudstone Curio, Crimson Kobolds, and Morophon, the Boundless

Prerequisites

• Beastcaller Savant on the battlefield
• Cloudstone Curio on the battlefield
• Crimson Kobolds in hand
• Morophon, the Boundless on the battlefield
• "Elf", "Ally" or "Shaman" chosen with Morophon

Steps

1. Activate Beastcaller Savant by tapping it, adding that can only be spent to cast a creature spell
2. Cast Crimson Kobolds by paying
3. When Crimson Kobolds enters the battlefield, Cloudstone Curio triggers, returning Beastcaller Savant to your hand from the battlefield
4. Cast Beastcaller Savant by paying due to Morophon
5. When Beastcaller Savant enters the battlefield, Cloudstone Curio triggers, returning Crimson Kobolds to your hand from the battlefield
6. Repeat

Results

• Infinite ETB
• Infinite LTB
• Infinite storm count