Adarkar Valkyrie, Intruder Alarm, and Altar of Dementia

Prerequisites

• Adarkar Valkyrie on the battlefield
• Intruder Alarm on the battlefield
• Altar of Dementia on the battlefield
• Adarkar Valkyrie does not have summoning sickness
• You control at least one additional nontoken creature

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, returning the sacrificed creature from your graveyard to the battlefield
4. When the creature enters the battlefield, Intruder Alarm triggers, untapping all creatures
5. Resolve the Altar of Dementia ability, causing target player to mill cards equal to the sacrificed creature's power
6. Repeat

Results

• Infinite LTB
• Infinite ETB
• Infinite sacrifice triggers
• Infinite death triggers
• Infinite mill
• Infinite self-mill
• Infinite untap of all creatures
• Infinite mana creatures you control can produce