Adarkar Valkyrie, Thornbite Staff, and Altar of Dementia

Prerequisites

• Adarkar Valkyrie on the battlefield
• Thornbite Staff on the battlefield
• Altar of Dementia on the battlefield

Steps

1. Activate Adarkar Valkyrie by tapping it, targeting another nontoken creature you control
2. Activate Altar of Dementia by sacrificing the creature targeted in step 1
3. When the creature dies, Adarkar Valkyrie triggers twice
4. Resolve the first trigger, untapping Adarkar Valkyrie
5. Resolve the second trigger, returning the sacrificed creature from your graveyard to the battlefield
6. Resolve the Altar of Dementia ability, causing target player to mill cards equal to the sacrificed creature's power
7. Repeat

Results

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