D&D 5E DM Advice needed Re Waterdeep

[UngainlyTitan]

Hi all, I generally run premade adventures and APs and am no good with homebrew, though I can allow the party off book. Often by switching into something else or borrowing levels in another adventure module.
I have run Princes of the Apocalypse to the conclusion and because the players wanted to continue to higher levels I had Halaster kidnap them and dump then in the lower levels of Undermountain.
After a few session tromping around in Undermountain, they have rescued some halfling travelling band and are taking them back to the surface. They are now at level 1 of Undermountain.

So what I need:

A reason for them to come back to Undermountain. I have been thinking of involving them in the machinations of the Shadowdusk family (Level 22 - DotMM) but I need more info in Waterdeep. So is Waterdeep: Dragon Heist worth it as a gazetteer. If not, what other source material on Waterdeep would you recommend and are there any other high level adventures you guys would recommend.?
Fantasygrounds compatible would be ideal and I am willing to consider converting from older editions.

 

[Fenris-77]

DHW does provide a pretty good set of info, and a ton of good adventure hooks that can easily be used outside the DH adventure narrative. It also includes Volo's Waterdeep Enchiridion, which is neat guide to WD written 'in-character' so to speak for the PCs. That said, I also have a ton of additional 3PP material that I use to paper over some of the cracks in the AP. Stuff I've used a bunch:

Here's to Crime - A Guide to Capers and Heists
Waterdeep City Encounters
Dragon Heist: Waterdeep Complete DMs Bundle
Durnan's Guide to Taverkeeping

That last one is super cool if you want to use owning a Tavern as a homebase. All the above are pretty specific to running heists and intrigue stuff and fleshing out DHW. From older editions, the obvious answer is City System.

 

[CodeFlayer]

If the players aren't interested in the Undermountain - have the mountain take an interest in them. Their rescue has caught the eye of a malevolent power that sends some minions to tag the players magically somehow (which they have the opportunity to thwart or detect)...

 

[UngainlyTitan]

I don't know that they are not interested but I like to have options.

 

[Parmandur]

Dragon Heist is a strong package of options for building stuff in Waterdeep.

 

[Eltab]

The 3e hardcover Waterdeep: City of Splendors provided me a sidequest during Rise of Tiamat: one noble house stole another house's griffon-riding gear (250 years ago!?) and as part of buffing up Waterdeep's defenses against flying foes they need every rider they can get.
This was another of the 'book of 1001 plot hooks' that 3e did so nicely.

 

[CodeFlayer]

I don't know that they are not interested but I like to have options.

smart

 

[Maxperson]

I don't know that they are not interested but I like to have options.

You could have someone or something in Undermountain steal something important to the group.

 

[pukunui]

FWIW you can buy the gazetteer from Dragon Heist separately on the DMs Guild: Volo's Waterdeep Enchiridion

 

[CubicsRube]

You could run dragon heist for a change of pace (it's quite a fun change of style from a typocal AP) but have the dragon hoard held in the lower levels of the dungeon.

Personally I'd look into the backstories of the players if you know them, and create some clues that something they are looking for or something tied to their past is also connected to the dungeon somehow. They can be different levels and reasons, and the clues can be scattered through a number of sessions so it seems to come about organically.

The main thing is to give the characters (and players) an interest in devling into the deep levels and finding whats there.