The Darkest Sparks

For the few minutes that the eclipse lasted, Luna could see small little purplish colored pops around her legs and feet. She payed them no attention, but once the eclipse ended, Luna looked down and the little "sparks" were gone. Luna, guessing that the pops were side effects of looking at the eclipse, just decided to walk back into her bedroom... but she couldn't! She could move everything but her legs. So she decided to just use her magic to fix this mess, but nothing happened... her magic didn't do anything either! Luna cried for help at the top of her lungs, but not a single guard heard her! The only pony that could hear the poor and desperate Luna was her sister, Celestia.

"What is this sound I hear?" Celestia thought to herself, but then it stopped... as soon as this happened, Celestia realized it was Luna. She ran to Luna's bedroom as fast as possible and pushed the door open, what she saw was horrifying, Luna wasn't there... then Celestia felt the same kind of feeling she experienced when Luna was banished to the moon... Loneliness.

Celestia quickly ran to her library, looking for the reason why Luna was gone this time. As she looked, she found a reference to another book which then referenced an ancient book which was written before Celestia's parents were even in existence!

Celestia wrote a letter to Twilight Sparkle, urgently asking her and her friends to go to the specified location that was explained in her book.
"My dear beloved student, Twilight Sparkle,

I need to ask of your help once again, my dear Luna has disappeared and in my library there was a book that referenced another story, but this one has been hidden away for millennia. Why you may ask, was this book hidden away and why for millennia? Well… that's because it was about something that even my parents had no idea of! Something extremely powerful."