Requires

Adarkar Valkyrie must be on the battlefield. Intruder Alarm must be on the battlefield. Moritte of the Frost must be in hand. Adarkar Valkyrie does not have summoning sickness. You control at least one legendary creature. Mana needed:

Steps

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

Results