Requires

Adarkar Valkyrie must be on the battlefield. Intruder Alarm must be on the battlefield. Vesuvan Doppelganger must be in hand. Mana needed:

Steps

1. Activate Adarkar Valkyrie by tapping it, targeting any legendary creature you control.
2. Cast Vesuvan Doppelganger 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 Vesuvan Doppelganger.
7. Resolve the Adarkar Valkyrie trigger from step 4, returning the legendary creature to the battlefield from your graveyard.
8. Put Vesuvan Doppelganger 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 Vesuvan Doppelganger to the battlefield from your graveyard as a copy of the legendary creature.
13. Repeat from step 3.

Results