Shepherd of the Cosmos, Kaya's Ghostform, and Yahenni, Undying Partisan

Prerequisites

• Shepherd of the Cosmos on the battlefield
• Kaya's Ghostform on the battlefield
• Yahenni, Undying Partisan on the battlefield
• Kaya's Ghostform attached to Shepherd of the Cosmos

Steps

1. Activate Yahenni by sacrificing Shepherd of the Cosmos
2. When Shepherd of the Cosmos dies, Kaya's Ghostform triggers, returning Shepherd of the Cosmos from your graveyard to the battlefield
3. When Shepherd of the Cosmos enters the battlefield, it triggers, returning Kaya's Ghostform from your graveyard to the battlefield attached to Shepherd of the Cosmos
4. Resolve the Yahenni ability
5. Repeat

Results

• Infinite LTB
• Infinite ETB
• Infinite sacrifice triggers
• Infinite death triggers