Need some encounter ideas for table of six 4th level PCs

[The Human Diversion]

If you're in my Wednesday night Faerun game, don't read any further!

don't read if you're one of my players:

Ok, so I have a home game set in Faerun and the PCs have been tasked with finding out why most caravans into the city of Waterdeep are being attacked. They have a day or two before they leave the city to investigate and I want to have one, maybe two combat encounters beforehand. What kind of things could adventurers encounter in the greatest city known at 4th level that wouldn't seem too contrived?

This campaign is heavily influenced by the Neverwinter Nights PC video games, so I had thought of having a noble approach the PCs and ask them to clean out a bit of an evil outsider infestation he has leftover from Mephistopheles having invaded Waterdeep (maybe have warring demons/devils in his basement?)

[Deadmanwalking]

Have them travel through the bad part of town for some reason and run into a street gang. An Otyugh in the sewers and various vermin swarms are also possible. All easily combined with the street gang if they lurk in the sewers...especially if they're were-rats.

Being recruited to attack such a gang is also fairly believable...or just running into them while doing something else.

[Kydeem de'Morcaine]

Bunch of homeless scavenger kids follow them at a distance.

When questioned, they say "The Old Man said peoples callin theyselfs venturers likeuns you guys often comes down with a case of the deads. Whosumper did ya will take yer shiny stuffs. But the Old Man said to grab whatere they didna sos we can sell it fer food. Nothin gainst you mister, but if yer gonna end up scraggled anyway, ya won need the stuffs."

That will tend to make the players nice and paranoid. As well as screwing up any plans to be stealthy or inconspicuous.

Have them get mugged or pickpocketed (or at least someone makes the attempt).
OR
Some tries to frame them for a mugging or pickpocketing.

[Kolokotroni]

One of the more interesting things to present to 'good' characters in an encounter is to put 'innocents' in danger, along with a threat to the pcs. Fires or other disasters work well here, you can go bigger scale but since these are side encounters, maybe a local gang/theives guild is setting fire to a local merchants home (with his family inside it) to get him to pay protection money.

Party has to fight the band of thugs but also save the family/stop the fire. Adds an interesting dynamic of problem sovling/skills/utility to the encounter.

[Nearyn]

Waterdeep encounter ideas:

Slavers stalk out of the dock ward by night, attacking people and dragging them into the shadows, never to be seen again.

A young gryphon breaks loose during training up on Mt Waterdeep and attempts to fly away, but gets its wing tangled and hurts itself. It manages to glide into the densely populated streets of the city below where people flee the frightened Gryphon's swiping claws, as the panicked creature tries to escape the city.

A group of mercenaries are picking a fight, relying on the relative scarcity of the waterdeep watch to not land them in trouble. A shame they decided to pick on a bunch of adventurers.

An alchemist had a lycanthrope brought in for study. He got careless. Now there's a werewolf loose! Everybody run!

A young man and his posse approach the PCs, having mistaken one of them for the cad who bedded his sister and then left her. The only warning is a shout of "There you are you fu**ing scoundrel! I'm gonna rip you apart!" and a rock being thrown, before the young man and his posse charge the PCs, saps and fists swinging.

Hope it helps

-Nearyn