"What vexes thee, sister?" Luna asked Celestia, who was sitting at a scribe's desk, staring confusedly at a sealed letter.
"This letter does. It is addressed to you, using titles that, as far as I knew, were forgotten to history, and it is sealed to your magical signature, so the Guards could not check it for harmful content." Celestia replied.
Luna frowned, and said "Then it wouldst be wise for me to open it here, where I have thine protection, and any harmful content can be dealt with accordingly."
"Let me notify the guards first, so they know we'll most likely be busy for a while, and they don't panic if we miss an appointment." Celestia said with a wry smile.
"Of course, dearest sister."
A few minutes later, Celestia returned with a smattering of guards, who took positions around the small room.
"Well then," Luna sighed, "Let us not put this off any longer." And with that, she unsealed the letter and started to read it.
Her jaw fell to the floor partway through the second sentence, and stayed there for most of the letter.
Celestia worriedly asked her if she was alright, to which she distractedly replied "Fine".
Luna's mouth worked over the oaths in the letter, as if not believing they were really written there.
Finally, she rolled up the scroll, and dazedly took a seat on a nearby chair. Celestia was instantly upon her, asking her if she was really alright, but instead of answering, she handed the scroll to her sister, and rested her head on her hooves.
"Wow..." was all Celestia could say after reading it.
"Verily" was Luna's reply.
"What do you think? " Celestia asked somewhat nervously. "Do you think they are truthful? Or do you think that it is a hoax?"
"Truly," Luna hesitantly replied, "I cannot imagine someone swearing those oaths in jest, for I could feel their magic from the parchment. And they were sworn of free will and sound mind, without any coercion or mind-altering substances."
"Well... This might be the second or third strangest thing happening to us in known history."
"The first is obviously Discord." Luna replied with surety. "Whether this ranks second or third depends on if you place the Bearers freeing me above or below this." She added more thoughtfully.
A guard burst through the door while they were still contemplating the ranking of the letter, startling them and the guards stationed in the room. He reminded the sisters of an important meeting with ambassadors form the Griffin Kingdom, which they were almost late for, because of the letter. They both agreed to shelve the letter until such a time when an appropriate reply could be formulated and written.
And as such, their lives went on.