A letter, lost in the depths of the Equestrian manuscrpts:
How do such things come to be? A destiny, found to be a dead end without a purpose. Was there a reason for my teaching? Or was I...not the prophesy? I thought I had found what I was here for, but that turned out not to be. I thought I had found the answer to bring all together in harmony again...but it seems I have brought nothing...but devastation.
Maybe Princess Celestia is right after all. Maybe I was a mistake.
And maybe she will find a new student more qualified than I.
"The rest of the letter is torn from here," said a voice as calm as the night itself. "I wish I would've known who had written it."
"You wouldn't have known it either way," said another, gentle voice. "This letter seems younger than a thousand years."
"Still," said the first voice, "I wish I would've known the writer. This manuscript has baffled me since the moment I have found it here in this ancient library." She referred to the dark, tidy, and small place in which was old, but well kept for.
"Well, wouldn't the Princess know?" asked the second voice. "I could get her-" She was stopped by the first.
"Cadence," she was told. "Celestia must never know of this place." Princess Cadence gave a surprised look.
"The great Star-Swirl the Bearded showed me this place," said the first. "This is where he kept the most secret of spells, in fact, everything he wrote was kept here. And nothing has left it."
"And..." hesitated Cadence. "Why can't Princess Celestia know about it? She is the ruler of Equestria, after all." The first put the old letter she was holding down, rolling it up neatly first with magic. She then faced Cadence with her dark eyes.
"I don't know why Celestia can't know about it for sure," she said. "But I must do what Star-Swirl told me about a thousand years ago."
"And what is that?" asked Cadence. The first sighed heavily before quoting the wizard.
"'Do not, by any means, reveal these secrets to your sister'."