“What have we here?” murmured Princess Celestia, as she strode into the Starswirl the Bearded Wing of the Canterlot Archives, past the scorch marks that refused to budge from Twilight’s mishap with time travel, and down one of the many partitions to finally stop at a door that had not been there the day before. The door itself was rather plain, a simple wooden affair, with a brass handle and an etching of Starswirl’s cutie mark on it, and an inscription above the door in Old Equuish that translated as ‘Do Not Open’. Celestia thought back as far as she could, and still couldn’t remember a room being built off the wing. But perhaps the records would prove more reliable than her memory. A quick summoning spell, and the most recent floor plan of the Wing in question appeared in the air before her, and revealed much the same as her memory. There was no room here, no door. She poofed the records back to their storage room, and focused on the door again. A detection spell revealed no hidden magic behind, around, or in the door. When trying to open the door magically though, the Solar Alicorn found that her magic could not get a grip on the handle, instead sliding right off as if it were covered with oil.
“Curious. Very curious,” said the Princess under her breath. Gingerly, she lifted a hoof and rested it on the equine handle. Experience had taught her that opening unknown doors quickly was not a good idea. Slowly, and very carefully, she began to push down on the handle, hearing the mechanism inside turning and retracting the bolt. Finally, after a surprisingly anxious minute for the Princess, the bolt released, and she pulled the door towards her, equally slowly, keeping the bulk of her body behind the relative safety of the door. Another lesson from experience, as this would let her push with her full weight if an eldritch demon was behind the door, and cut it off from entering the world. Once the door was fully open, though, what she found silenced her.
Nothing. The door was just that. A door. It lead to nowhere, and when opened like now, simply revealed the wall behind it. A hoof probed the wall, just to make sure it wasn’t a thin sheet. It wasn’t. However, on the inside of the door was posted a message.
“Got you! –Princess Luna.”
~~~time~~~
Celestia giggled. Then it devolved into a chuckle, and finally she was rolling on the floor, howling with laughter. This lasted several minutes before the solar princess managed to compose herself, and get up again. Once she did, she closed the door, and summoned a peice of parchment and a quill, and began to write.
“My Dearest Twilight, ...”