The End of the Story. Sort of.
Rincewind trudged through the halls of Unseen University glumly. It took him some time to identify at least one of the emotions he was feeling as boredom - he'd often expected it would be a sort of contented feeling, not a restless one, so it took him some time to identify it.
Despite the aid of nearly half the faculty of the University, and no small number of students as well, Star Swirl had utterly failed to come up with a means of returning to his home. Then, one morning, the Librarian had come up with a way of doing it.
It all came down to Sourcery, he had explained. Or, rather, Horsery. When Coin the Sourceror realized he could no longer remain on the Disc, he had simply opened a gate elsewhere and strode through it, closing it behind him. No one knew precisely where he had gone, and he had never been heard from again, but in this particular instance that probably boded well, rather than ill. Why could not Celestia and Luna do the same thing?*
It had taken very little preparation after that. Star Swirl had spent many evenings between the All's Fallow and that fateful day when the Librarian had presented his brilliant (though sparsely worded) idea regaling the two alicorns with tales of his homeland and the other two Pony Kingdoms, so they were nearly as familiar with its geography, flora, and fauna as he.
Consequently on one day, nearly a week and a half prior, Star Swirl, Celestia, Luna, Rincewind, the Luggage, Conina, Nijel, and the Librarian had met on the University Grounds. The sun shone brightly down upon the city of Ankh-Morpork - brighter, in fact, than it had at any time prior to the unusual events surrounding the recent All's Fallow Eclipse - which only served to make the contrast between the cheery lighting and Rincewind's sombre mood that much more poignant.
Yes, he thought, his friends were leaving him, possibly forever, but they were going home. Did that not make this a happy occasion at all?
Apparently, he concluded, not.
After a tearful** farewell, the two alicorns had touched their horns together, thought longingly of the land of ponies, and brought their horns apart and down, drawing out an arch in the form of a rainbow***. As soon as the ends of the rainbow touched the ground of Unseen University, there was a brilliant light and Rincewind noted the tell-tale vibrancy of colour that indicated Horsery at work, driving away all of the octarine in the area. In point of fact, given the wide radius of the colourful effect, there was quite a lot of it, which helped soothe the raw ache in Rincewind's... he paused, wondering what it was that was hurting. Possibly his spleen? Not that he had any idea what a spleen was, or what it did, apart from, he had once been told, ooze green. Well, this felt like a sort of oozing pain, didn't it? His spleenache, then, he decided with a nod. That would do.
Smiling tearfully, the alicorns looked around at their new friends. "Thank you all," Celestia said, hugging each of them in turn.
"Thank you, especially," said Luna, "Rincewind the Brave." She hugged him tightly, as though afraid to let go.
Then, the three ponies had separated from the humans (and Luggage), stepped through the Rainbow Portal, and vanished, along with the Portal itself.
* To be perfectly fair, what he had actually said was "Ook," but his point was understood well enough.
** And also, it must be admitted, hug-filled.
*** Lacking in octarine, however, it could really only be thought of as most of a rainbow.
All of that had been nearly a week ago, however, and Rincewind still had that spleenache. He missed Celestia, and Luna, and Star Swirl, and even - though they remained not only in the world, but in the city of Ankh-Morpork itself - Nijel and Conina. Only by having all of his friends together, he concluded, would the hole in his spleen be filled.
So it was that his rambling, melancholy footsteps took him down into the Unseen University's Library. He had spent a lot of time there over the course of his stay at the University. He and the Librarian had become friends long before the arrival of ponies to the Disc, and would likely remain friends long after, though the word itself had been somewhat foreign to them prior to this particular adventure.
He stepped into the Library, intent now on suggesting a trip down to the Mended Drum to drown their sorrows and console each other over their mutual spleenaches, but the idea of doing so quickly fled his mind as soon as he crossed the threshold.
Something, he could see, was wrong.
The books, first of all, were listless. Even Euricades' Enumerated Entreaties. The Librarian was frantic, scurrying about the place, trying to cheer them up. A new tome, bound in pink with nearly as many spangles as a good wizard's hat, followed him around like a sort of hardbound puppy, waggling its spine and attempting to cheer up its fellow tomes. Rincewind stared curiously at it. "The Wholly Booke of the Pink Pony of Deathe," he read aloud. As though it had heard its name being called, the book turned towards him, bounded twice, and then was upon him without seeming to have crossed the intervening space,* lapping joyfully at his face with its bookmark.
"Oook," said the Librarian, and the book relented.
"What..." Rincewind looked around. "What is going on," he asked, "and would it be any use running?" He was genuinely at a loss on this second part, which only added to his confusion.
"Oook," the Librarian said, shaking his large, shaggy head.
"Well," Rincewind said, feeling a bit of his old pluck, "if you don't know what's going on, then running is still on the table, isn't it?**"
"Doubt it," said an unfamiliar voice behind Rincewind. He yelped, leapt into the air, and had whirled to face his unknown assailant before it became clear that he wasn't actually being assaulted.
* In point of fact, it had not crossed the intervening space. Holy tomes, in a world as magically suffused as the Disc, tended to take on characteristics of those they were dedicated to.
** To be clear, running was no longer on the table, having scarpered long before the initial question had been asked.
"Who the bloody hell are you, and how did you get in here?" It was a valid question. As Unseen University was a school for wizards, and a wizard was defined as the eighth son of an eighth son, there were certain characteristics a wizard was expected to have.
The stern-looking woman in wizard's robes (with a staff and everything) sighed and rolled her eyes. "It's only me, Rincewind," she said.
Rincewind stared at the young lady, uncomprehending. She looked familiar, yes, in the sort of way that she looked completely unfamiliar but not quite. Perhaps it was the fact that he had never seen a woman on University campus before, especially a middle-aged one, that made her difficult to place. She could be one of the kitchen or cleaning staff, he concluded, though she looked a bit too young to be - or was it too old?
But no, he thought, she clearly had a wizard's staff, albeit without a knob - whoever heard of a wizard's staff without a knob on the end, anyway? - and no member of the University's less magical staff would have one of those.
"Ook!" said the Librarian helpfully.
"I'm sorry, who?" The name was familiar, he knew. But where from? "I've heard the name, Miss Smith -- it is Miss Smith, isn't it? -- but I can't place where."
Eskarina sighed, brushing a stray lock of white hair out of her eyes. "Same old Rincewind," the old woman muttered. "Anything unusual or seemingly out-of-place, and off you scurry for your hidey-hole."
"OOK!" the Libarian said forcefully.
"Really? What, just recently?" Eskarina Smith tilted her head curiously and examined the ratty wizard with renewed curiosity.
"Oook ook ook."
"Well, then." She smiled. "I suppose I owe you an apology."
"What for?" Rincewind said. "It's not like you've said anything that wasn't true."
Eskarina frowned. "Argh," she muttered. "None of this matters anyway. Hullo, I'm Eskarina Smith, and yes, I'm a wizard, and you're Rincewind, who is also a wizard, and we are all" - and here, the old woman made a grand gesture encompassing the whole of the University, and implying quite a bit beyond as well - "in a great deal of trouble."
"Of course we are," Rincewind muttered. "I take it running is off the table?"
"All of reality will be about to have unravelled," Eskarina said sternly. "Where would we run to?"
"Never you mind to," Rincewind said as sternly back at the young lady. "In my experience, that takes care of itself. It's the from that's the important bit. Well, and the running."
He blinked, taken aback, while both Eskarina and a now-terrified Librarian waited for the implications of what the Disc's only female wizard had just said to settle in.
"Wait, did you say 'all of reality'?"