Adarkar Valkyrie, Thornbite Staff, and Ashnod's Altar

Prerequisites

• Adarkar Valkyrie on the battlefield
• Thornbite Staff on the battlefield
• Ashnod's Altar 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 creature you control
2. Activate Ashnod's Altar by sacrificing the creature targeted in step 1, adding
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. Repeat

Results

• Infinite colorless mana
• Infinite death triggers
• Infinite ETB
• Infinite LTB
• Infinite sacrifice triggers