A glimpse of a possible future.

"Dear Twilight Sparkle,

This past day, you may have heard that Canterlot was to be evacuated. You may even have heard some brief speculations as to why - Discord escaping once more, a number of changelings that had evaded their eviction, or perhaps even the return of Nightmare Moon. Of course, these three dangers have all been rendered toothless; you and your five friends saw to that.

We have purposely kept certain details from the populace at large, and will continue to do so for as long as we can. Upon learning the truth of the matter, many ponies would not act rationally, and panic solves nothing. However, it is imperative that you know what has happened, and that you tell nopony but the other five bearers of the Elements of Harmony and your assistant. Enclosed is an officially sealed missive, entitling the bearer to commandeer a train to transport seven individuals to Canterlot from Ponyville. Make use of it as soon as you possibly can. Should it prove ineffective, send a message through Spike and I shall react accordingly. If I do not hear from you by the next sunset, I must assume the worst and will come to find you posthaste.

The catacombs beneath Canterlot are deeper than anypony knows. I tell you this not to appeal to your scholarly tendencies, but to caution you. Hidden beneath the ground are secrets that have been lost to history, sconced in ruins so old that even I have no memory of them. There have been some few expeditions mounted to search for the forgotten past, each carefully approved by Celestia and myself, but none had returned, so we discontinued the practice. I now fear that we have not been cautious enough. We wished to lose no more ponies to the darkness, but if we had continued to search for answers, perhaps this may never have happened.

Apologies, I digress. Recently, a single earth pony emerged from the catacombs, starving, diseased, and near death. We were unable to save his life; the blight was unknown to our most accomplished physicians, and though he may have fought it off, he had not the strength. We mourn his loss as we mourn the others, but we were able to learn something of the explorers' fate before he expired. He spoke of a sealed portal, locked away with magical wards so ancient, naught was left but frayed scraps. The air about the portal was filled with the taint of decayed black magic, those few fragments remaining still potent enough to overwhelm anypony that came too close. And yet, they all felt a strange attraction. None could approach, but none would leave, even as their supplies dwindled. What came afterwards, he would not say, other than that the portal was opened, and that he fled.

We do not know how he survived to return, with no food or water. Perhaps his determination to bring a warning sustained him, or perhaps the answer is not one we wish to know. Regardless, it is obvious that his experiences changed him. Even had he lived, he would never have been the same pony that entered those ruins, months ago.

The following day, immediately after dawn, my sister entered the tunnels herself, so troubled by what she had heard that she felt she must act personally. She left me to manage Canterlot for the day, and gave her assurances that whatever she might encounter, it could not keep her from her celestial duties.

She did not return to lower the sun.

That was yesterday. I called the evacuation after raising the sun myself this morning, hoping that Celestia would return before night was to fall, but knowing that I must prepare for the worst. I cannot afford to wait any longer. I could, perhaps, conceal her absence for a few days, but it could not last. Thus, I have only one course of action left to me.

I ask you, not as a princess, but as a sister: Help me find her.

~ Luna