Adarkar Valkyrie + Intruder Alarm + Mirrorhall Mimic // Ghastly Mimicry

Adarkar Valkyrie

Intruder Alarm

Mirrorhall Mimic // Ghastly Mimicry

How it works

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

This clever loop relies on the constant state-based removal of the legend rule to repeatedly trigger Adarkar Valkyrie and Intruder Alarm. By having Mirrorhall Mimic enter as a copy of your legendary creature, you trigger the legend rule, sending one copy to the graveyard while Adarkar Valkyrie's active delayed trigger and Intruder Alarm's static untap ability respond in kind. Each time Intruder Alarm untaps your creatures, Adarkar Valkyrie resets to target the alternate copy currently in the graveyard, allowing you to seamlessly ping-pong the permanent back and forth indefinitely.