Adarkar Valkyrie, Intruder Alarm, and Protean Raider

Prerequisites

• Adarkar Valkyrie on the battlefield
• Intruder Alarm on the battlefield
• Protean Raider in hand
• Adarkar Valkyrie does not have summoning sickness
• You control at least one legendary creature
• You have attacked this turn
• available

Steps

1. Activate Adarkar Valkyrie by tapping it, targeting any legendary creature you control
2. Cast Protean Raider by paying , choosing to have it enter the battlefield as a copy of the legendary creature targeted in step 1
3. Put the legendary creature into your graveyard due to the legend rule
4. Adarkar Valkyrie and Intruder Alarm trigger
5. Resolve the Intruder Alarm trigger, untapping all creatures
6. Holding priority, activate Adarkar Valkyrie by tapping it, targeting Protean Raider
7. Resolve the Adarkar Valkyrie trigger from step 4, returning the legendary creature to the battlefield from your graveyard
8. Put Protean Raider into your graveyard due to the legend rule
9. Adarkar Valkyrie and Intruder Alarm trigger
10. Resolve the Intruder Alarm trigger, untapping all creatures
11. Holding priority, activate Adarkar Valkyrie by tapping it, targeting the legendary creature
12. Resolve the Adarkar Valkyrie trigger from step 9, returning Protean Raider to the battlefield from your graveyard as a copy of the legendary creature
13. Repeat from step 3

Results

• Infinite death triggers
• Infinite ETB
• Infinite LTB
• Infinite mana creatures you control can produce
• Infinite untap of all creatures