The library was aflame, its staff and patrons alike using spell and storm to try to control the blaze. Nearby, a broken spire smoked, its stones embedded in the countryside. The night was beginning to fade, but the moon still held reign above.
In a hidden courtyard, a white alicorn was oblivious to it all. She struggled silently with a monumental task. Staring at the horizon, she willed the sun to rise. Begged it. Pleaded with it.
Something spoke in the darkness. “Is my sister having trouble?”
Celestia staggered, forgetting her spell for a moment. No one but Luna should be able to approach her, here. The voice sounded like her sister, but... different. Darker. Treacherous. She glanced about, looking for the one who spoke.
“Above you, dearest. Really, now, did you forget what those wings were for, after all those chariot rides?” The figure that appeared before her, landing in the courtyard, was most definitely not her sister.
She was taller, thin, and clad in silver-blue armor. Her mane and tail flowed as Celestia’s own, but took the form of a blue mist studded with stars. The Sun Princess stared a moment, and then demanded, “Who are you? What are you doing here?”
“Why, don’t you recognize me, Celly?” Her voice was a serpent, lying in wait. “It’s your beloved sister.” Her words hardened, daggers in flight. “Or did you forget about me too?” The intruder’s mane and horn flared a brilliant white, and Celestia found herself against the columns lining the wall of the palace.
“How dare you strike me?” She stood, and flared her wings wide, channeling her own abilities outward. “And what have you done with Luna?” She channeled a restraining spell: a sphere meant to snare and capture. The intruder laughed, each pitched note acid on Celestia’s ears. From within the crystalline bubble, her horn flared again, and she blinked to her sister’s side.
The Sun Princess recoiled, and reared. The intruder circled, but Celestia turned to keep an eye on her. “Sister, sister,” she chided. “You showed me how to escape that trick eons ago. I’ve always been an apt pupil.” She sneered. “But now you can learn from me!” She spun on her forelegs and delivered a blow to the princess’ chest, staggering her, dropping her to her knees.
“Luna?” she gasped. “Is that really you? What happened to you? What have you done?”
“Done? Why nothing, dear sister. Not yet, at least. I simply want your ponies... our ponies... to see my wonderful night.” Celestia struggled to her hooves, and found herself face to face with the creature with her sister’s voice. Their eyes locked, and Celestia could not look away.
“Forever.”