The Docks are the main port of entry and exit for maritime travel and transport to and from Lüm. Dozens of vessels come and go every day. Most of these ships carry relatively innocuous cargo and passengers, but if someone or something dangerous does arrive in Lüm by sea—a cursed object, a malevolent wizard, etc.—the Docks are where they'll first land, and where their effects are likely to first manifest.
Example: A ship recently arrived from Idora had an unexpected passenger—while there one of the crew had been possessed by a gorel, a type of creature that can transform others into monstrous servitors. After the ship docked, the gorel changed hosts, but it's there somewhere on the Docks, causing problems through its transformed servants. Can the PCs find the gorel and put a stop to its mischief, ideally without harming its servitors until they can be restored to their original mind and form?
Though the Docks, away from the shoreline and the main roads, are largely ignored by the Lüm and the Port Authority and are riddled with crime, most of that crime is on a relatively small scale, and victimizes other Docks residents rather than the city at large—which isn't to say the PCs may not still have a motivation to stop it, particularly if they have friends in the Docks or live there themselves. Still, sometimes operations centered on the Docks do have a larger impact beyond, making them an even bigger target for PC investigation.
Example: A small-time thief in the Docks named Kort the Squirrel got lucky and robbed the right cart and ended up with a staggeringly powerful magicalorb with which they can call down lightning, cause earthquakes, and create similar phenomena. Now he's using that orb to blackmail the city government, and the PCs have to stop him... and prevent the orb from falling into the hands of a more experienced and resourceful villain who can make more effective use of it and pose an even greater danger.
Thanks to the vigilance of the Port Authority, there may be less crime along the shores and the main roads of the Docks... but when something criminal does happen there, it tends to be much more significant. Hijacking large merchant ships, grand theft of valuable cargo, sabotage by Djarvin's enemies...
Example: A passenger cruise ship, the Lady's Honor, was supposed to arrive yesterday morning, but there's no sign of it. The most recent communication from the ship came a few hours before its expected arrival, when it was close to Lüm and still on schedule. In fact, the Lady's Honor has been stopped by a powerful, greedy wizard who froze the ship in place, placed an enchantment of invisibility on it to make it hard to find, and is currently trying to threaten some of the wealthy and well-connected passengers into revealing their valuable secrets...
The many warehouses of the Docks are used for temporary storage of cargo that's about to be loaded onto outgoing ships or cargo that has just arrived on incoming ships and has yet to be distributed to its final destinations. Nobody goes into the warehouses except the staff of the shipping companies and the carters who move the cargo... and perhaps the occasional thief looking to make a score. That makes the warehouses ideal places to hide secrets, and while the vast majority of the warehouses are no more than they appear, a few of them might hide secret cults, the headquarters for criminal operations, laboratories for reckless magical experimentation, and more...
Example: The shipping company Platinum Logistics has been falling on hard times lately, and with the smaller volume of its shipping it hasn't needed to use all its old warehouses... and was only too happy to lease one out to a renter. Unfortunately, that renter, Annarann Iune, is a necromancer who wanted to use the warehouse as a place for her to carry out her creation of undead, and to store her undead creations for later use. She's gotten a bit careless, and a few of the weaker undead she made have escaped and started wandering the neighborhood, which is where the PCs come in. If they can find out where the undead are coming from, maybe they can put a stop to Iune's operations before her ultimate plans come to fruition... or before her more powerful undead escape and start causing bigger problems...
