So, the players had requested a chance to do something outside of the main dungeon. I fully support this: a change of scenery, a change of pace, and a chance to try out some situations that wouldn't come up in the main quest. So with a quick refresher on the background, they departed Roslof and made their way to the Lich's Library. This is something that we came up with early in the campaign, like so:
"Favorite bit of semi-OOC interaction: Firstborn remarked that they had to be the weirdest adventuring party in the Keep. They're not, though they're definitely off in the right direction for that. But that gave me the chance to tell them about The Librarian. The Librarian is a Lich who lives in a small complex in the forest, about eight miles outside of the town. He pursued magical knowledge and power and eventually attained undead immortality so that he could finally finishing reading and writing all the books that he wanted to read and write. With the right letters of introduction, his library is a god-send to anyone doing research. He is the sort of librarian who keeps his library quiet and calm, and in fact he can enforce magical silence through the entire complex. The players were absolutely charmed to know that this place existed, and at some point they're almost certainly going to have to pay it a visit."
Later in the campaign, the Mousefolk Cleric and the Dragonborn Sorcerer had a letter sent to the Lich, asking permission to visit and do research on some sort of guard-dragons; the Sorcerer received a response a few days later while out and about in the town, when he and the Halfling Rogue were attacked by a skeletal minotaur. Upon slaying the undead monstrosity, they found a note tied to the inside of its spinal column indicating that the lich found their request acceptable. (Some of you may be wondering if I lifted this method of epistolary from the Elder Scrolls games; the answer is absolutely yes.)
So, the group arrived at the library and was unpleasantly surprised to find another skeletal minotaur standing at the gate; but this one led them back to the library proper (the largest of the buildings in the complex) and then returned to the gate again. They stood around inside until the Lich arrived to greet them. The lich is about what you'd expect: a tall, skinny human, now withered and slightly rotted, with burning red eyes. He led them through the library, past a beholder that floated in the midst of a circle of stands, apparently reading six books at once; then past a cyclops who had stopped to remove her monocle and wipe it clean, and then into a back room where he pointed out an empty shelf. "You see my problem?"
The group confirmed that they did.
"I loaned it to a wizard," the lich explained. "Loaned it to her, and she left without returning it."
"What kind of book was it?" asked the Swashbuckler.
"A spellbook, of course."
"Wait..." said the Barbarian quietly. "That whole shelf was for just one book?"
"I can't keep it beside other books," answered the lich. "It might interfere with them."
"So you want us to get your book back," asserts the swashbuckler.
"Yes. You must retrieve it before it takes over the wizard. And if it does take over the wizard, you must kill her and then bring it back."
"This book... it doesn't have spells that open portals to the plane of elemental fire or anything, does it?" asked the Swashbuckler.
"Not that I know of. If it does, it has never mentioned them."
"Right," said the Sorcerer. "Get the book, kill the wizard if needed, and bring the book back here. Any idea where she went?"
"I asked around," said the lich, "and they were seen in the town of Graindale, a few miles west of here. I do not know where they went after that."
So the group makes a quick decision, and heads for graindale.
Graindale is a town only in the loosest possible sense of the word. It has three buildings: a blacksmith, a sort of general store, and a tavern that doubles as an inn for the few travelers who come through town. Our heroes head for the tavern.
The main room is small (about the size of my kitchen), with four small tables and a small bar at one end. Behind the bar is woman about seven feet tall, maybe three hundred pounds -- most of it in her shoulders. "Ah!" she cries. "Adventurers! Welcome to the Inn of the Dulled Axe!" Sure enough, there's a massive bardiche on the wall behind her, with a strip of thick leather covering the edge of the blade. She is, obviously enough, a full-blooded orc... but while the party is still gaping, a small half-orc comes toddling out from behind the bar.
"Ah!" Cries the Barbarian. "So cute!" He rushes over to the child, who immediately holds out his hands to be picked up. The barbarian scoops up the child, cooing and fussing over him.
"Careful," says the orc inkeeper gently. "We call him Sam. I'm Arlis." They're between meals, but they still have some stew on for anyone who wanders in, and some bread that isn't yet stale. The group decides to eat, and she hauls over a massive pot of stew and sets it on the table (which creaks dangerously) before ladling a good-sized scoop into each of their bowls. Her husband, a middle-aged human, emerges from the kitchen behind her, bearing a tray with the bread and some spoons for them to eat with. His name, it turns out, is Bildur.
They haven't seen any sentient magical spellbooks, but there was a wizardly sort -- a human woman -- among a group of adventurers who stopped in a week or so earlier. They don't normally eavesdrop on their guests, but this group got a little loud and Arlis remembers overhearing that they were bound for Stonereef and would be meeting somebody from Isonwood there.
They've heard of both these places before. Stonereef is a predominantly Dwarven town, known for its mining, smiths, and metalcrafts; there's a much of the city underground as there is on the surface. The name Stonereef has something do with a geological peculiarity of the location, but they're not sure exactly what; it's one of those bits of terminology that makes perfectly good sense to Dwarves -- of course you'd name it that -- and not much sense to anybody else. Isonwood is unusual in being a community primarily of half-elves; it does some trade in lumber (but limited, so as not to damage the forest) and has a thriving artistic community.
The group finishes their meal and heads on to Stonereef. It's an irregularly-shaped walled city on the top of a hill or low plateau, with three stone ramps leading up to three large gatehouses. The group has caught a ride on a turnip-farmer's wagon, but they're pulled aside by a Dwarven guard at the bottom of the ramp. (The horses will have an easier time on the ramp without them anyway.) Stonereef, he explains, is a town of law and order; if they had mounts, they would be responsible for any messes made by their mounts. The same for golems, familiars, and companion animals. There's to be no stealing, no killing, no brawling, and no disturbing the peace. The group assures the guard that they're extremely easy-going and heads up the ramp.
Just inside the city there's a batch of small stalls, carts, and individual sellers. The one that catches their eye is a gnome who's selling wind-up mechanical spiders. Everybody buys one, and I'm sure we'll have spider-races to make important decisions at some point. A young dwarf -- they can tell by the lack of beard -- peels himself off the wall and approaches, offering to show them around the city for the very reasonable rate of two coppers a day. There's a brief discussion of whether he means "act as a guide" or "give them a tour", and he's perfectly willing to give them a tour -- but that would cost a silver each. Instead, they engage him as a guide and ask about places to stay.
Stonereef has three inns: The Golden Bowl is the nicest, and also the most expensive, where the most successful merchants and occasional visiting nobles tend to stay; The Shattered Box in the warehouse district, which caters to itinerant workers and is the least expensive, especially for extended stays; and the Frothing Otter, which is in the trade district near the central market, and offers a respectable place for lesser traders and occasional adventurers to stay.
The group decides that the Frothing Otter is their best bet, and has their guide lead them there by way of the central market.
That was it for today's adventures; I've worked up character sheets for the wizard and her party, so it'll be adventurer versus adventurer if our heroes manage to track them down next week.
 It's also a reference to Eve Forward's Villains By Necessity. Firstborn gave a distinct side-eye when I named it.