Shepherd of the Cosmos, Altar of Dementia, and Kaya's Ghostform

Prerequisites

• Shepherd of the Cosmos on the battlefield
• Altar of Dementia on the battlefield
• Kaya's Ghostform on the battlefield
• Kaya's Ghostform attached to Shepherd of the Cosmos

Steps

1. Activate Altar of Dementia 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 Altar of Dementia ability, causing target player to mill cards equal to Shepherd of the Cosmos' power
5. Repeat

Results

• Infinite LTB
• Infinite ETB
• Infinite sacrifice triggers
• Infinite death triggers
• Infinite mill
• Infinite self-mill