The way the candle light cast stark, dancing shadows on the walls of her bedroom was the memory Twilight would hold most keenly of her third night living in the palace.
The first had been a rush of excitement and exploration, and the sleep of contented exhaustion after a long day finding her bearings.
The second had been unmemorable.
On the third, she had woken from a nightmare in which her whole family were chained in darkness, as a cackling, black-coated monster had swallowed the sun whole and cast down the walls of her room to reveal an onyx cage, that glistened in the light of a thousand burning stars.
To wake to a room cast all about with thin, black shadows had made her believe the dream was real, if only for a moment, until the Princess had spoken comforting words to her in a voice soothing as the warmth of the morning sun on a chilled back. The words had retreated from memory, but the feeling was one she could never forget.
The next morning, when she awoke again, she found Celestia still sitting by her bed, as if she hadn't moved all night. Surely she must have left at some point? Surely she had better things to do?
So Twilight had asked her, in the way only a sleepy child can: "Princess, what is a Princess for?"
She'd squeaked in terror and burrowed under the covers the moment the words had left her mouth. Asking a princess what good she served was a capital crime, surely? But no punishment had been brought upon her head. Instead she heard laughter. Not mocking, or cruel, but caring and soft.
When she emerged from beneath the sheets, she found Celestia smiling down at her.
"You mean, my student," the Princess said, "what purpose does a Princess serve?"
"I guess."
"Perhaps you can answer this for me, young Twilight. What purpose does a Princess serve? What makes me a Princess? Think on it today, and answer tonight, if you have any answer at all."
And then she had turned and left, humming a song that Twilight thought she recognised, but had never been able to recall since.
The day had passed in a flurry of activity, as Twilight was introduced to servants, to rooms of study and libraries and the more of the grounds of the palace but the question was never far from her mind.
That night, as the sun sank toward the horizon, Celestia returned to Twilight's room, that in her memory seemed so large and empty, but that was nevertheless small enough that the Princess dwarfed everything within it.
"Did you remember my question, young Twilight?" She seated herself by the bed and smiled. "What is a Princess for? What makes me a Princess?"
Twilight had pondered this, tapping her chin as she had seen her parents do when they thought hard about a question. Of course she already knew the answer, but it was right to show that you were thinking about it even so.
"You're rich and powerful," she said. "You control the sun and moon, and have a huge palace, and lots of guards and servants who you tell what to do."
And with the answer given, she had grinned at Celestia, and Celestia had smiled back at her. Then, slowly, she shook her head.
"These are all things that a Princess can do, or that a Princess can have. They are what a Princess can be made of. Truly I am powerful, truly my magic is powerful, truly I have servants and wealth, and the ability to move the sun, but this is not what a Princess is for, nor does any of it make me a Princess."
"Oh," Twilight had said. To say she had been disappointed was to fail to grasp the reality of things.
As if to sense her anguish, Celestia had bowed her head to Twilight. "You are wise beyond your years Twilight Sparkle, even if you have not yet fully understood the truth this question will one day reveal, nevertheless you understand that a Princess must wield power, and must command, and must do her duty to her ponies. As I must now do my duty to you, as I train you. Sleep well, my young student, and dream of warm meadows and peaceful days."
Onyx. She'd learned that one from a foal's story book that she'd found in the palace library on her second day. Perhaps it hadn't been so unmemorable after all.
* * *
For the first two years of her education, Twilight had lived two days at the palace and five at home with her family. By all reasonable accounts the arrangement was intended to give her time to adjust to her new station, but Twilight eventually came to understand that it was to prevent her becoming isolated and insular, a tiny cog in the machine that was the royal court, divorced from the toings and froings of the everyday pony.