Professor Kirke gets up and follows Nightmare at a brisk walk.

"And why would our presence be required, and by whom?"

She starts leading him outside. "I met Peter Pevensie in -- call it a nexus between worlds, of sorts. There is a deadly problem on my world that you, he, Lucy Pevensie, Susan Pevensie, and Edmund Pevensie may be able to help with. He requested I gather you, on the principle that five heads are better than one, so to speak."

Once outside, she looks around and grimaces. "I cannot teleport to a place I've never been, so we shall have to do this the long way. Get on my back." Nightmare's not totally sure this is going to work, but she's seen young dragons do it to their quadrupedal parents, so it can't be that hard. Certainly less hassle than holding him, and eventually three more humans, in her magic the entire way.

He pauses and looks around.

"That might be rather easier if you could stand by that bench, ma'am, I think I'm somewhat too old to climb a Horse all the way from the ground."

"Here." She grabs him up in her magic and sets him astride her back, just past the junction of her wings. "You may keep hold of my peytral, should you fear falling." That said, she recasts the invisibility spell, though they won't look any different to each other.

Professor Kirke squeaks in alarm as he's lifted. The sqeak turns into a laugh partway through.

He adjusts his position on Nightmare's back, and indeed grabs her peytral. Fortunately, he has (a little) experience with this sort of thing.

"Well, this brings back memories. Lead on."

She orients herself and takes off, heading to the next nearest school. An impatient part of her wants to go as fast as possible, but it would not do to send a wave of night crashing over the countryside in the middle of the afternoon, with a trail of murky stars leading directly to her eventual location.

Instead, she says, "You have met an alicorn before? I would find that hard to believe, but a great many unbelievable things have happened today."

"I haven't met an alicorn before, no. I take it that is your type of creature? I was under the impression the term referred only to the horn. But in any case, I have not in fact encountered any form of unicorn before but I did once ride a winged talking Horse when I was a boy."

"It does, to the soft cap covering a foal's horn that falls off shortly after birth. Somewhere across the centuries it got confused, and it's certainly shorter than 'winged unicorn.' Largely the conflation exists to annoy obstetricians.

"If that pegasus was anything like the ones from my world, I won't ask why you specified 'talking.' Never met a pegasus with anything resembling a brain-to-mouth filter, Celly was--" She stops abruptly and her small smile vanishes. "Never mind."

"That seems like a peculiar confusion- but then, perhaps no more so than our using a word for lettuce and spinach which originally referred to salt. In any case- what's this problem you need to deal with, and what might an old professor be able to do about it that the kings and queens of Narnia can't?"

"We haven't asked the kings and queens of Narnia because apparently there's no reliable way to get there from here. I'm told someone named God governs the realm and has a fair amount of power, should he be persuaded to bring it to bear, which from what I hear also seems unlikely. Equestria's affliction is - hmm. In simple terms, the sun is no longer circling the planet, and I cannot gain control of it to continue its regular orbit."

Apparently she doesn't know about the Pevensies' station. Well, he isn't going to spoil the surprise.

"Oh dear. That sounds inconvenient. Is it night or day?"

"Night over Equestria, day over the other half of the planet. --Here we are. If I render you visible, will you be able to retrieve the others quickly, or will they take convincing?"

He will be able to, and does, at least for the Pevensie brother who's at this school.

"We're to mount you, ma'am?"

She makes a face. "Not if you say it like that, you're not. You must be Edmund Pevensie; Peter Pevensie told me Susan Pevensie and Lucy Pevensie would be together." She picks up both humans in her magic and settles them on her back again, Edmund behind Kirke.

"I must say," Nightmare adds offhandedly as she recasts the invisibility spell and takes to the air, "I'm sure your parents are wonderful po--uh, people, but they could have been a bit more creative with your second names. Or at least made them shorter."

"Them being English, that would have been rather unconventional. 'Pevensie' is the name of our father's family.

But what was the urgent business Professor Kirke said you were here on?""

"I suppose that is how some of the earth pony clans do it, with whatever crop they grow. Still, what if there's--" She shakes her head. "Never mind. The sun is dead. I can't move it around the planet, so we need to either figure out a way to do that or evacuate everyone. Your brother thought you would be of help."

"Narnia, or some other world?"

"Apologies, I should have specified. Equestria is the land I rule. I don't know what other creatures call the planet, but our name for it is Equus."

"What is Equus's sun made of? What holds it in place? How did it move when it was alive?"

"I can see why Peter thought to ask for you," she says, stalling a bit. "There's -- the way is--" She stops and takes a breath. It doesn't really seem to help. "My sister Celestia moved the sun, and I the moon. Before we ascended, teams of unicorns did the same, though the working was such that all but one gave up their magic for it. You'd never find the volunteers for it in this day and age."

"Ascended?"

If she's relieved that that’s the question he chooses to ask, she doesn't show it. "Became alicorns and, incidentally, princesses. We were supposed to be convenient political figureheads." She twists her mouth in a wry smirk. "Didn't last long."

"And there's no-one around who can ascend into your sister's place, magically speaking?"

"Unfortunately, no. The process takes years, and even if we somehow found a candidate, there's no guarantee they'd have any affinity for the sun. They could very well have bubbles or butterflies for a cutie mark, and then where would we be? Back at square one, with some powerful idiot tottering around like a newborn foal and getting in the way."