Twilight Sparkle yawned widely, plodding thankfully for her bed. The coronation was done, she was now the Princess of Friendship, all her friends were back to normal, and she could finally get some r-"Come Twilight Sparkle, there are urgent matters we must discuss."
Luna stood in the doorway, wearing a no-nonsense expression and holding a cup of something that smelled too strong to rightfully be considered coffee. Twilight blinked, "Now? Can't we just... rest for the day? We've been celebrating all night-"
"You are at your most vulnerable when you are resting or celebrating and I did say these matters were urgent so... no."
"No need to be snippy, it's just been a long day."
Luna sighed, rubbing her temple tiredly, "Indeed. I apologize Twilight, it has been an even longer day for me. And some of what I am about to tell you is very... personal for me. And now that you have ascended, very personal for you." She continued somewhat bitterly, "As usual, sister took on the glamorous role, empowering you with the power of an Alicorn while reminiscing over an aesthetically pleasing slideshow. It falls to me to explain some of the more... inconvenient realities you are now faced with."
Twilight's newfound feathers stood up slightly in apprehension, "Like what?"
"Like..." She sighed and blurted out the next sentence as though that might make it more palatable, "Alicorns are not allowed to eat."
Silence reigned between the two pony's for several long moments before Twilight chuckled, "I can't believe you actually had me there for a second."
"I am not trying to 'have you', I am telling the truth! Tia and I agreed, long ago, that we would not allow ourselves to consume food. Or drink, if that needed to be clarified."
"Ok... so what's with the coffee?"
"Prop." Luna turned the mug upside down, the cup filled with 'coffee' yielding nothing but a small cascade of steam.
"Huh." Twilight shook her head, "But every living thing needs to eat food to fuel itself and drink to keep itself... hydrated."
"Every mortal thing needs to eat food and drink water. We do not. We can of course, but we suffer no consequences for abstaining."
"Ok, but Princess Celestia loves cake. Like, LOVES cake."
Luna gave her a patronizing look, "She appears to love cake because it's her favorite illusion to project when she's doing something she's not supposed to be doing. Did you never consider how single minded she was when there was a 'cake' in the room? Half the time she isn't even in the room in question. Tis my understanding that, when I was gone and she was taking double duty, she often napped during her meals."
Twilight pondered all the times she'd informed Celestia of critical information while she had been eating cake. Including when she'd explained her theory over the circumstances of Luna's return. A small continent's worth of perceived guilt suddenly shifted from her mentor's shoulders to hers.
Luna didn't take notice of her appalled expression, "Anyway: No food whatsoever. We learned that the hard way. Several times."
Twilight's ears perked up, half at the promise of ancient historical insight and half because she needed the distraction, "Somepony tried to poison you?"
"No. Well, yes, but that was less of a learning experience and more of an amusing diversion. Pony's would try every few hundred years and either Tia or myself would be treated to glorious hallucinations while the other got to enjoy watching us converse with said hallucinations."
Twilight gawked.
"Oh don't be dense Twilight. We're immortal. Poison, no matter how thoroughly vile the effects, is but a momentary distraction. No, the day we stopped eating or drinking was the day some madpony realized that being an immortal goddess does not inherently make one immune to mind affecting substances. Just... very, very resistant. On the outside. When something tries to mind-control us from the inside... (sigh)... Well, you remember the first time we met."
"You mean, when you were Nightmare Moon? So this is a recent rule? Relatively, I mean."
"Not really. We made the rule of no eating thousands of years before our banishment, when sister had consumed the potion in question. Fortunately, the art of potion making was much more of a guessing game back then and Tia was simply frustratingly belligerent rather than outright evil. We were able to... contain her while the guards found and beat the would-be controller till he spilled his guts. Naturally, it was absolute hay getting any information out of him then so it took nearly six months to brew a remedy that worked and another two weeks to convince Tia to drink it."
Luna shook off the thousand yard stare she'd worn while recounting the memory, "No, the circumstances of 'Nightmare Moon' were somewhat different and they bring me to my next point: Breathing is on a strictly need-to-speak basis."
There was a pause as she allowed Twilight a moment to wrap her head around that.
"-until you learn how to adequately use telepathy that is."
"What?!"
"Breathing is a critical weakness that your lessers will exploit. Don't do it."
"But I have to breath, I mean, come on!"
"Nope."
"Seriously?"
"Yes."
"You're messing with me again, aren't you."
"I never messed with you to begin with but I wish that I were. I very much miss the scent of flowers."
"...but we're talking right now!"
"You are talking. I am miming. And projecting my thoughts into your head. Celestia visits your old room when she feels lonely." The last sentence sounded exactly the same but Luna's lips had stopped moving.
Twilight's jaw fell open.
...
...
"...does she really?"
"Oh for Sister's sake Twilight, that's not the point."
"Ugh, fine, but we're talking about that later." She filed it away in her Questions for Luna folder, behind the questions she was about to ask and in front of 'what did you do on the moon for a thousand years?'. She'd never gotten up the courage to ask the latter. Based on the truth-bombs she was getting in this conversation, she probably couldn't handle the answer.
"You project your thoughts out all the time? How can you filter them? And why even bother moving your mouth at all? And you're seriously trying to tell me that you haven't taken a breath in 1,000 years?"
"Yes. I don't. It's disconcerting. And sort of." Luna answered, in order, without opening her mouth. Twilight shivered. She was right: it was disconcerting.
Luna elaborated on the last bit, "Obviously, I didn't breath on the moon, but I have not taken a breath since you freed me with the Elements and my sister brought me up to speed in the aftermath."
"Horseapples."
"You watch your mouth in this castle Ms. Sparkle. If you're so convinced, why don't you prove me wrong?"
"What? By holding my breath till I pass out?"
"You are now an Alicorn. You have all the abilities thereof. You physically cannot asphyxiate."
"Fine! I will."
They stood there for almost an hour before Twilight was forced to concede defeat.
"Ok. Maybe I don't need to breath. But I still think this whole thing is ridiculous."
"You shall think it less ridiculous when you are banished to the moon for ten centuries."
"...don't you mean, if?"
"Thou art immortal Twilight, tis a very long time indeed. I do not doubt your dedication but none of us manage to be perfect forever."
Twilight blinked.
"If it makes you feel any better, I once sent Tia to the sun for a year when she was getting overly despotic. Fear not-" she quickly added upon seeing Twilight's expression, "We do not do that anymore. It is... most unpleasant. When you are imprisoned, it will be no worse a place than the moon. It really becomes more of a vacation after a while, you almost meditate the centuries away-"
Twilight rubbed her forehead tiredly with a hoof, "Can we please move on to the next lesson. And can you please start moving your lips again?"
Luna smirked, "The last time we heard that was under very different circumstances."
Twilight shuddered, "Ugh. No wonder you always seem so awkward. You really don't censor any of your thoughts?"
"Apparently we are not the only one." Luna's mouth resumed its movement, "Yes and no. We leave out the non-verbal thoughts. Putting it all together would be overwhelming for you and embarrassing for me."
A look of dawning comprehension crossed Twilight's face, "Is that what the 'royal canterlot voice' really was?"
"Oh, goodness no. The royal canterlot voice is my normal thought level. This is whisper-thoughts."
"Whisper. Thoughts."
"Quite."
"...how can a thought have volume?"
"LIKE THIS."
Twilight reeled back, the voice so loud she'd swear it would shake dust from the ceiling, "Ok, ok! I get that you can do it, I just don't understand... how?"
"It has to do with how much attention you divert to who you're speaking with. And, of course, with the fact that we are divine beings many millennia old. " She snorted, leaning in conspiratorially, "I once made a changeling's head explode by giving it my undivided attention while saying hello."
"First of all, gross. Second of all, doesn't that mean you're basically ignoring me right now?"
"Ooh butterflies!" Luna cantered through an archway into the gardens.
Twilight pressed her lips together and took a deep breath through her nose, "I already regret knowing this."
She followed.