Broken, Weak, Shameful are the emotions Celestia felt at the time Nightmare moon returned with Sombra, tirek, and chrysalis. Using magic forbidden to even her parents, she summons help... with a price.
With Sombra's return, he was able to release tirek with a shaky alliance they traveled to the badlands and with chrysalis in toe they stormed canterlot, they were prepared this time, no nonsense.
They separated the elements of harmony they weren't able to stop them. And in my foolishness, I agreed to let luna hold them off whilst I prepared the failsafe teleport spell in order to teleport the surviving civilians to safety. What a fool I was, once the teleport went off luna was corrupted into nightmare moon once again by Sombra.
Now, I am alone in a failsafe room in the castle dungeons, my citizens spread far and wide, the elements of harmony missing I only have one choice left. I must summon Him.