Hofri Ghostforge, Mistmoon Griffin, and Altar of Dementia

Prerequisites

• Hofri Ghostforge on the battlefield
• Mistmoon Griffin on the battlefield
• Altar of Dementia on the battlefield

Steps

1. Activate Altar of Dementia by sacrificing Mistmoon Griffin
2. Mistmoon Griffin dies, triggering itself and Hofri Ghostforge
3. Resolve the Hofri Ghostforge trigger, exiling Mistmoon Griffin from your graveyard and creating a token copy of Mistmoon Griffin that has "When this creature leaves the battlefield, return the exiled card to your graveyard"
4. Resolve the Mistmoon Griffin trigger, returning nothing from your graveyard to the battlefield
5. Resolve the Altar of Dementia ability from step 1, causing target player to mill cards equal to Mistmoon Griffin's power
6. Activate Altar of Dementia by sacrificing the Mistmoon Griffin token
7. The Mistmoon Griffin token dies, triggering itself twice
8. Resolve the Mistmoon Griffin token's trigger granted by Hofri Ghostforge, returning Mistmoon Griffin from exile to your graveyard
9. Resolve the other Mistmoon Griffin trigger, returning Mistmoon Griffin from your graveyard to the battlefield
10. Resolve the Altar of Dementia ability from step 6, causing target player to mill cards equal to Mistmoon Griffin's power
11. Repeat

Results

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