Adarkar Valkyrie, Thornbite Staff, and Yahenni, Undying Partisan

Prerequisites

• Adarkar Valkyrie on the battlefield
• Thornbite Staff on the battlefield
• Yahenni, Undying Partisan 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 Yahenni 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 Yahenni ability
7. Repeat

Results

• Infinite LTB
• Infinite ETB
• Infinite sacrifice triggers
• Infinite death triggers