Adarkar Valkyrie + Intruder Alarm + Protean Raider

Prerequisites

• Adarkar Valkyrie does not have summoning sickness.
• You control at least one legendary creature.
• You have attacked this turn.

Steps

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

Effects

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