A maid dipped herself in a formal way, reminding Umbra of Purple Polish so far away. "The sisters await you at meal. Please follow me."
They walked alongside her, at least until Morning spotted something. "There's one of them." They were passing a stained window of some ancient event. "Is that a dragon?" It seemed Celestia was keeping it at bay with some sort of magic. It was hard to tell the specifics, with stained glass, but the ponies around her were shielded by her presence.
The maid paused as those she led did. "Celestia wards the dragon lord," she read of the plaque at the bottom of the glass. "She is a fine and noble ruler. We're lucky to have her."
Shifting nudged against her daughter-in-law. "We'll visit others like this, tomorrow. I hear they come in all kinds of varities."
Umbra considered it, but was slowly moving past it all the same. "Are they all of Celestia?"
"Goodness no." The maid propelled herself down the finely carpeted hallway. "Any important event, involving Princess Celestia or not, gets recorded for us all to see. Princess Twilight adorns quite a few, often with her friends."
Morning sped up to be at the side of her family. "These are more than one thing at once."
"Clever." Umbra smiled with pride at her daughter. "Pretty sure they are. Historical markers, fond memories, and a bit of national pride, all rolled up into one big stained glass."
"Right here." The maid knocked once with a firm clop. "Umbra and her family," she called through the wood, then stepped away. "Have a pleasant time."
Shifting stuck out her tongue at nothing specific. "Disadvantage of famous relations, you become 'and friends'." She waved Umbra towards the door. "You first, Princess."
"You're my princess." Umbra nipped at Shifting's ear on the way by, to both's smiling approval. She opened the door to find a much larger dining room than the one she had visited in the dream. Perhaps that made sense, with both royal sisters in attendance, one at either side of the long table. A test?
She couldn't sit near either of them without sitting far away from the other. Or did she pick a spot near the middle with moderate distance to both sisters? Hm.
Morning made a decision without a hint of a pause. She hopped up next to Luna. "We're here, as you requested. Thank you for not repeating that offense."
Celestia blinked at that start. "Offense? Sister, did I miss something?"
Luna let out a strained laugh. "Foals... I visited Umbra's dream. That is where I repeated her invitation and shook her free of the north for us."
Umbra sat next to Morning, and Shifting next to her. Shifting looked over the selection of food curiously. "Breakfast and dinner?"
Celestia smiled at that. "It is a different time for us both. For me, the last of the day. For my sister, the first. You are welcome to either as you please. Now, it sounds like you may have forgotten that I had also invited you, Umbra. If you still wish to investigate the mirrors?"
Umbra started. She had forgotten! "I have a lot to do... Thank you for the reminder." She willed a heavy tome from her pocket, hovering over to settle in front of Luna. "Spells, as promised. Exploring my dark magic has become something of a hobby of mine, and turning them to productive ends wherever I can manage it."
Luna willed the book to open before her. "A treasure trove of shadow magic, good and terrible."
Morning grinned with pride. "Mostly terrible, I imagine."
Shifting reached a wing over Umbra to give Morning a poke. "Your mother enjoys being nice."
"Why?"
Umbra blinked at that blunt question. "Because it makes me happy to make others happy."
"Ah." And that was apparently good enough. "Reveal your magic." She was looking to Luna with that.
Luna barked out a laugh at the firm request. "Your foal is full of spirit, and malice."
"Thank you." Umbra colored at that 'compliment' as Morning looked proud. "We are trading though, right?"
"We are." A new book popped into being. "This tome was given to me by my sister." Luna met eyes with Celestia. "When I returned from my... time-out... I was weak, small, and confused. This book showed me how I could be close to others even when I was awake in the night."
Umbra started. "Woah! You're letting me see the whole thing?" She hadn't expected that.
Celestia inclined her head faintly. "Umbra is correct, this is a large step. Are you certain?"
Luna turned a hoof back on herself. "Time. You don't have it. You have occupied your days with a thousand concerns. Even with this knowledge, you will not take my duty away from me. I realized I was being petty about it, snarling at anypony that looked curious... As a creature of nightmare and darkness, this magic is as much belonging to you as I. That you are gentle of temperance and loving of other ponies seals the deal, as it is said."
Celestia clapped her forehooves in one firm strike of metal on metal. "I am so proud of you, sister. Then a fair trade." She poined at the two books. "Shadow for shadow. I hope you both enjoy what you learn from each other."
Morning was watching Celestia. "You're not curious? Shadow is a frighteningly powerful force."
"It is," Celestia allowed. "But so is light. I am a princess of the sun. Studying shadow magic runs counter to me in large part. I do know a tiny bit." She winked at the filly. "The brighter the light, the deeper the shadows it can cast."
Morning applauded in slow steady clops. "I like that. Do you have any magic to trade? My mother is an eager collector."
Celestia considered that with a soft hum. "Well, she will likely be quite busy learning what Luna has provided, to speak nothing of offering assistance where Luna may need it. It would be rude to get in the middle of that with both ponies in such eager exchange. Perhaps afterwards?"
Luna nudged Umbra's book. "Does this mean you have lost all real desire to find your way home? You have a choice right now to seek it, or learn more magic, and that choice seems clearly made."
"It's complicated?" Umbra tucked the book she had been given away out of sight. "I've started a life here, and I like it. The life I left behind is... Taking it up now would be hard, and returning to a place that hates me. The pony world side eyes me sometimes, but it celebrates me in the end."
Morning looked between her mother and Luna. "What world do they speak of?"
Shifting chomped some of the breakfast fair that was close to her, on merit of the family being closer to Luna. "That's a secret! Up to your mom if she wants to talk about that."
Celestia raised a hoof. "My apologies. I had assumed, incorrectly, that you were all informed."
Umbra looked divided. "I wasn't specifically trying to keep it from Morning."
"Please share then, mother."
"But it's also complicated and weird." Umbra shrugged softly. "And mostly irrelevant when it comes to her."
"If it involves you, mother, then it can't be irrelevant." A simple statement of fact, spoken as if reminding that Tuesday follows Monday.
Celestia smiled brightly at the exchange. "I do not have my neice's eyes, but the love between you doesn't need magic to see. It warms my heart to see."
Umbra's horn glowed as she squeezed her daughter gently. "What did I do to get such a perfect family? And you wonder why I'm not rushing to leave it... Alright, since you're curious... Mother is not from this world."
"What world are you from?" As if that fact was simply accepted. "Is it one of light, or shadow?"
Umbra frowned with thought. "I never thought of it that way before... It had its bright points, but plenty of shadow to go around. Twilight? Let's go with twilight. Compared to this world, dim, but that may be unfair. This world seems especially bright." She pointed to Celestia. "It has a sun princess that may be part of that."
"I do what I can." Celestia dipped her head, ears spread to either side. "But darkness yet remains. I appear to be enjoying supper with two examples as we speak."
Morning set a hoof on her chest. "We are good examples of the darkness."
Umbra nipped her daughter's closer ear. "Fearsome, but approachable. In that world, there was only one speaking species. All the others were below them. They didn't have to learn to get along."
Morning crossed her arms. "Is that how you became such a fierce fighter, mother?"
Umbra was about to snap a quick reply, but was caught short. "Hm... You may have a point... I prefer to make friends, but I will defend those friends from anything that threatens them."
"They will learn the folly of angering the darkness." Morning seemed sedately pleased with her mother's words.
Shifting offered a sweet pastry held with her wing thumb towards Umbra. "She took that all well."
"As if I expected less from my daughter." Umbra grinned, getting a chance to turn Morning's words on her. She chomped the offered pastry. "Mm. But not as good as the dream?"
Luna lifted an ear. "In the dream, you simply tasted 'something especially good, the best you ever had'. There were no specifics. You didn't actually taste anything." She smiled at her sister from across the table. "Still, I imagine she would like to know. How does it compare to what they serve up north?"
Umbra looked between the royal sisters she had become a small machination of. "Cadance has good chefs, and so do you. They taste different, but that's a matter of local supplies and taste, not quality. You just don't eat northen food without crystal berries, for instance."
"How very... diplomatic." Celestia was smiling despite any unspoken complaint there. "I am happy to hear my niece is being properly fed. She oversees less ponies than me, but the job can be just as stressful."
Morning perked her small ears. "That's what tasted different. I'm used to crystal berries."
Shifting pointed at Morning with a wing. "Did you know she only recently started eating regular food?"
Morning colored just faintly. "That is a personal matter."
Umbra squeezed with her magic. "She's a trooper. We've expanded her diet quite a bit and now she destroys any food stupid enough to give her a chance."
"Their first mistake was being there." Morning sat up with pride. "Their second is their lacking defense."
Celestia laughed gently. "I should imagine mealtime would be far more complicated if our food tried to defend itself against us."
Luna stood with Umbra's book hovering over her. "I should get to work, then study this. Umbra, are you staying in town? If so, I will consult you if required, and you may do the same. I will instruct my guards to see you to me." She paused suddenly. "I'm being foalish. That book isn't to leave Canterlot. For as much good as I have worked with it, it remains forbidden magic. If it is not held by an authorized pony, the only other place it would reside is with the other forbidden tomes."
"All the good spells!" wailed Umbra, imagining the amazing spells that lurked within that forbidden hall for her to study, were she not denied... Still, that meant she had at least one forbidden book. "I will treat it carefully, and return it when I'm done, promise."
Morning inclined her head slowly. "You can practice it on me, mother. Then you can witness me."
Umbra blinked at that invitation. "I witness you all the time, usually proudly."
Morning waved a hoof and shook her head in counterpoint. "You have not seen my nightmares."