Adarkar Valkyrie, Intruder Alarm, and Carrion Feeder

Prerequisites

• Adarkar Valkyrie on the battlefield
• Intruder Alarm on the battlefield
• Carrion Feeder on the battlefield
• Adarkar Valkyrie does not have summoning sickness

Steps

1. Activate Adarkar Valkyrie by tapping it, targeting Carrion Feeder
2. Activate Carrion Feeder by sacrificing itself
3. When Carrion Feeder dies, Adarkar Valkyrie triggers, returning Carrion Feeder from your graveyard to the battlefield
4. When Carrion Feeder enters the battlefield, Intruder Alarm triggers, untapping all creatures
5. Resolve the Carrion Feeder ability
6. Repeat

Results

• Infinite LTB
• Infinite ETB
• Infinite sacrifice triggers
• Infinite death triggers
• Infinite untap of all creatures
• Infinite mana creatures you control can produce
• Infinite +1/+1 counters on Carrion Feeder