"What are her conditions?"
Luna was lying on a table, in the middle of a room underground, one of the spaces which had survived the battle. A room not unlike the one the Heart had been housed in, where it had activated upon Nightmare Moon and Twilight's departure and helped with the cleansing of the storm. A room not unlike the one the black box Sunburst had created had been stored in, along with the scales within it. A room at that moment occupied, aside from the sleeping alicorn, by her sister, that sister's former student and heir to the throne, and three doctors of the brightest that could have been brought there. No one else was there, and nothing else was there but the table Luna was on and the medical equipment focused on her.
And the response came, same as it had come before. "She's asleep," one of the doctors said. That was that, all there was. Luna slept, but she did not wake. For hours by then, for days to come the others knew. She would not die from it, but neither would she wake up. The pain Celestia felt was so great Twilight chose to comfort her, if modestly so. It outdid her due punishment.
Luna looked different. Not in her features, not in her body miraculously healed of its wounds, but in her mane. Towards the base, where connected to her skull, there was a red tinge to it, purplish even, flowing and flaring. Like the dawn, or the sunset, a hint of sunlight in her night sky. None of the presents understood it fully, but they all understood its depth. Powerful magic, deep, ancient, beyond the reaches and confines of study and method. Primal, far too close to the essence of life to be jotted down in mere parchment and ink. The nature of souls was as frightening as it was fascinating, and no more than a glimpse into it would they be able to glean from what they were there witnessing.
Regardless, Luna slept. Dreamt, perhaps. Who to call, when the Dreamwalker was stuck in her own world, who to reach her with? Her student, of course. Had she had one, it would have been no question. Did she have one?
She had something. Not quite a protégé, not quite a groomed successor. She was unlike her sister in many ways, and in that she was no different, consistently she was not as her. She had someone. Someone recently taken under her wing, someone who had learned from her more than anyone alive, less than few throughout history. Rainbow would be called. She'd be asked to search for her mentor, in the world of dreams. That was clear. That was the only solution.
It did not please anyone. It did not please Celestia, to know her beloved's fate in the hoof of a mortal who yet knew of her realm and magic more intimately than she. It did not please Twilight, too alike her old teacher not to feel the slight of envy at being by a pegasus outdone in such a field of magic. It did not please the doctors, to see their science useless and outdone by what even for scholars of magic like them was esoteric. Perhaps, however, it did please Luna. Was that the case, did anything else matter?