Luna woke stiff and slightly disoriented. Mentally noting that sleeping on her lounging cushion is much less comfortable than lounging on it, she rose and drowsily made her way to the washroom to refresh herself. Then a sudden clear thought shot through her mind as she splashed water on her face.
Twilight! It's the middle of the day!
In her sleepy disorientation she'd completely forgotten that it wasn't still night and had left Twilight without a source of moonlight. She dashed back into the room expecting the worst, but instead skidded to a shocked stop at the sight of Twilight passed out and glowing with moonlight of her own.
Part of being royalty is learning not to show emotion, even unexpected emotion, unless one desires to do so. However, nothing could have prevented the slack-jawed stare on Luna's face as she fought to process the relief, amazement, curiosity, and awe she was feeling.
Twilight must have passed out while writing, as she lay sprawled out on her cushion with her head partially resting on a half-filled scroll, a quill not far from her mouth. A tiny background portion of Luna’s mind labelled that as “adorable,” but the focus of her attention was elsewhere. Soft moonlight poured out from Twilight and her dark hair shimmered as it shifted back and forth in a non-existent breeze. Slowly, one half-step at a time, Luna made her way back to Twilight. She couldn't seem to get her mind to function and had to check half a dozen times to ensure she wasn't dreaming herself.
Upon reaching Twilight, she was able to make out the small smile on her sleeping friend's face and it brought one to her own. Luna was used to thinking of Twilight as cute, both in appearance and personality, but she thought that Twilight asleep and glowing with that small smile on her face was the most beautiful thing she had ever seen. She’d seen herself in the mirror when channeling moonlight plenty of times, but seeing it like this – seeing Twilight like this – was completely different. Without conscious thought, a hoof reached out and stroked from just behind Twilight's ear down to her shoulder...
...and suddenly cute and adorable were fighting for priority as Twilight released a sound somewhere between a murr and a purr. Suddenly snapping back to herself, Luna blinked and fought back a series of giggles.
Did she really just purr?
Repeating the gesture did indeed get another purr.
I can’t wait until Tia finds out about this, she thought as she let slip a giggle. Assuming she doesn’t already know… It’s just too adorable for words!
Spellbound by Twilight for a whole new reason now, Luna continued petting Twilight's neck. Caught up in her giggles at this unexpected facet of her friend and imagining her sister’s possible reactions, she failed to notice that the purring had stopped until she heard a sleepy, "Luna? What are you doing?"
Snapping back to herself once again, Luna felt her face heat up as she locked eyes with Twilight. "Ah... Twilight... I was just trying to wake you so we could move to the bed. It'd be more comfortable than sleeping on the cushions."
"Oh-kay..." Twilight glanced toward Luna's foreleg which was still rubbing the base of her neck.
Luna's face grew even hotter and she jerked her leg back. "My apologies. I got distracted."
"Distracted?"
"Uh..." Ack! Think of something! Glancing away from Twilight's eyes she realized she did have a way out of this one. Best to have an excuse prepared in the future… "Look at yourself... You’re providing your own moonlight."
The next few nights were very busy. Twilight had determined that channeling (not producing, as it turned out) moonlight was actually a very simple matter once one realized it was possible. It was essentially a self-sustaining effect and would continue on its own until cancelled – or until something interfered with her magic flows. A fact which explained how Luna had been able to sleep without fear that she'd stop providing moonlight for her.
No, channeling was the easy part to figure out. Harder to explain was how she could do it in the first place. Channeling moonlight required Lunar magic according to Luna, and Luna was the only one with it. Even Ursa didn't channel moonlight. Instead, they fed on moonlight and produced starlight from it. Which basically means that she has a medical condition which should only affect Ursa and an ability to channel moonlight which should only be doable by Luna.
Makes perfect sense...
Twilight sighed and rubbed at her eyes. Luna was back to holding her night courts again - with a few precautions in place to ensure nopony got too close. She still didn't want to take chances of contamination even though Twilight was fairly certain it couldn't be passed on through ordinary means. Granted, she had to admit that Luna had a point when she said that they really don't know yet what constitutes "normal means" for whatever this is.
Flipping through her research notes on the topic only served to further frustrate her. She'd learned a great deal about Ursa recently: a second trip to see Majora while Luna was at night court had answered a lot of questions and filled in a lot of blank spaces from the few books available on the subject, but nothing seemed to answer the question of how she’d gotten into this situation or how to get out of it.
There were only ever two Ursa in existence at one time, a major and a minor. If a minor died, the major would condense some of its consumed moonlight to birth a new cub. Twilight thought that it was a combination of moonlight and shadow involved, but couldn't be sure without witnessing the process. If a major died, then the minor would reduce its output of starlight and convert moonlight to mass instead, until it grew large enough to be considered a major and could birth a new cub. Majora had implied that if both died that the stars would guide the birth of a new Ursa, but couldn’t (or wouldn’t) give any further explanation.
Cubs were born unable to generate starlight. More accurately, they had no spare moonlight to expend on the creation of starlight. For the first few weeks, months, or years (getting accurate times was proving difficult) they would be placed in a location exposed to moonlight as much as possible by the mother. During this time, they were not in danger of pain or death when not exposed to moonlight or starlight, but still couldn't face the sun. After enough feeding and growing, excess moonlight would begin being converted to starlight and the cub would gain its signature forehead star. This is the point that failure to be exposed to appropriate levels of moonlight or starlight could become fatal. It still couldn’t produce enough starlight to sustain itself for some time after that point though, and the mother had to provide for it.
Twilight knew there had to be something obvious she was missing here. Whatever the condition was, it didn't affect newborn Ursa. That seemed to point to it being passed on from the mother at some point. But how?
I'd probably have it figured out for now if it weren't for Luna, she muttered internally.
She was even more distracted by Luna than ever of late. Two more times since the first, she had been awakened from dreams of Luna by the same stroking of her neck. She couldn’t deny that it was a very pleasant way to wake up…if only it actually meant what she wanted it to mean. Twilight had to struggle to hold back the desire to blurt out her feeling each time, as Luna would just give her the reason for waking her and move on with things. It was just so new and felt so nice that she just wanted to believe that, just maybe, Luna...
No! She shook her head sharply. You've been over this plenty of times. She's just a friend. Just a friend...
She gave a ragged sigh and buried her face in the cushion. She didn’t want to face that fact, and Luna's tendency to shift in her sleep to nuzzle into her neck didn't help her resolve at all. They both channeled moonlight as they slept now. Twilight insisted that she was fine doing it herself, but Luna wanted to be on the safe side just in case. After all, there was no reason that Twilight should be able to channel it in the first place and she could lose the ability just as inexplicably.
She slammed her hoof into the cushion beside her head in frustration. It just didn't make sense. If she still had Luna's power from when Tirek attacked it would make sense, but she didn't. Tirek had taken it all, and then the Tree of Harmony had restored all the stolen magic directly to the rightful owners afterward. Celestia certainly wasn’t left with any of Luna’s magic after returning it. The only way she could think of it being possible for her to use an ability tied to Lunar magic was...
She jerked up in surprise as a number of tiny details suddenly clicked into place and a new hypothesis was formed.
It’s just barely possible…and it would explain…
She had to verify! She quickly scribbled a note to Luna in case she was late returning, and vanished in a brilliant flash of light.