You were HOW old?
"You were really raised by Starswirl the Bearded?"
Celestia looked up from her tea in surprise. She was not surprised that Twilight would ask about that topic, but rather that there was a wariness to it, compared to Twilight's usual filly-like enthusiasm when it came to anything Starswirl.
Twilight fidgeted in her seat at the silence. "I'm sorry Princess, but I was just doing some thinking now that all the excitement's over, and I have some questions, if you don't mind?"
Celestia smiled. "Oh Twilight, you know you don't have to be so shy about questions. There is no such thing as a bad question and I'm always happy to answer yours. And yes; Starswirl raised myself and Luna, in the Castle of the Two Sisters. I barely remember the time before we knew him, we were so young. Oh, and the lessons Twilight, the lessons! You would have loved them! He taught us everything he knew. Though, I suppose now, you can grill him on magic directly, if you'll pardon my Griffon."
Twilight perked up, wingtips fluttering in excitement, but she quickly pulled them back in. "Oh yes, I've got so many scrolls full of topics I...I mean, ahem, I just wanted to ask...how old were you and Luna when the Pillars were sealed in Limbo? Comparatively, I mean; to a normal pony."
Celestia's smile became just the tiniest bit brittle. "I think...oh, let me see now...I was always just that little more developed than Luna, and she had just started reading independently...a few years younger than your friends' sisters, I believe. Neither of us had quite grasped what death truly meant, in the sense of 'never coming back'; we waited so long for Starswirl to return and- Twilight, are you quite alright? You're looking rather pale."
Twilight grinned a little too wide, her hoof tracing nervous circles on the table. "Hehe, no, I'm fine! But, uh...remember when Tirek really started to come back and we sent Discord after him? Something you said really...well, it threw me worse than a buck from Applejack." She inhaled sharply, taking a book embossed with the stylized golden head of a unicorn out of her saddle bag and flipping it to a certain chapter.
"So, you were explaining about Tirek…that his brother Scorpan came to know friendship-" she flipped the illustrated pages as she spoke, until she put a hoof on one in particular. "-and befriended Starswirl the Bearded."
She swallowed, not daring to look up at Celestia.
"And then Scorpan told you and Luna of Tirek's intentions before returning to his homeland, while Tirek was arrested and jailed in Tartarus."
In this picture, the Chimera-like Scorpan stood supplicating two adult Alicorns.
Twilight's tail swished behind her nervously. "Princess, I...look, I really don't want this to add up! We've just established that yourself and Luna were extremely young when the Pillars were sealed, but before that, the both of you were already ruling Equestria! At the least, Scorpan came to you two about Tirek and not the Pillars, who would still have been around!"
She was pacing now, shoulders tense and voice gradually rising in volume.
"And! When Starlight asked the Pillars about Stygian, they said that they were all living together in the Castle of the Two Sisters! Two foals. Have. A Royal. Castle. Complete with Guards, considering we found bits of armour and helmet all over the place before we gave up trying to clean it up. I even found your foalhood diary about you and Luna playing in the secret passages!
No, I'm getting off-track a bit here.
Oh yes! The Pillars were all living in the Castle with you. Yet you and Luna never met them. You only had Starswirl, and maybe a few guards, I don't know, but you were completely isolated!
And then! Here's the clincher; the Pillars make a brave and noble sacrifice, yes, but they left two, mentally and emotionally immature foals, to run Equestria."
Deprived of precious oxygen, Twilight abruptly and sharply inhaled, with a high-pitched wheezing sound.
"I just...thinking about the Crusaders having to run Equestria by themselves, I...no, I'm not even going there."
Celestia found herself examining the gold of her shoe. Herself, Luna and Cadence all had them, as well as peytrals, but Twilight did not have one. Celestia, herself, felt as naked as a freshly-reborn phoenix without them, because she had never not worn them, save to sleep. She was Alicorn, a Princess, it was her right to such finery and a symbol of her duty to the ponies of Equestria. A duty that never ended, and one she didn't even fully remember taking up. She scarcely remembered those carefree days of just her, Luna and the guards running through the Castle's secret passages; she'd have to ask Twilight if she still had her diary.
Speaking of Twilight, she had finally collected herself, and Celestia felt no small measure of pride as her (former!)student gathered her courage and stared her down.
"Princess...Celestia, please understand. I'm 96.7% certain that Starswirl was...uh, grooming you and Luna to rule Equestria in the manner of Foal Monarchs of the Ancient Unicorn Tribe. I'm not entirely sure why though, having met him now; he didn't seem at all like he wanted to be a Shadow Regent and seemed quite happy about your current status."
Celestia had already made the same connections Twilight had, but emotionally, she was floundering. Before Starswirl and the Pillars had been sealed, she and Luna had been, the admittedly unofficial, rulers of their little corner of pre-Equestria. But after the sealing, that had been when the newly-united Three Tribes had come to their little land of friendly, accepting towards all, ponies of all kinds. Even the nocturnal Thestrals and Crystal Ponies on the North border. The leaders of the Three Tribes had come to the two fillies, apparently acting on a suggestion made by Starswirl as the Pillars had passed through their lands, asking to be joined under the banner of the Two Sisters in neutrality.
Celestia was starting to recall it more clearly now. Blank flanks. That was what a disappointed Princess Platinum had called them in the heat of the moment. The two of them didn't even have Cutie Marks!
Celestia turned her mind to Twilight's half-gasped, throwaway comment; the Crusaders running Equestria by themselves? Her stomach turned a little at the thought. How irresponsible. And cruel.