Thanks for the suggestions, folks.
I have fleshed out the adventure quite a bit and will now be working on the succubus sub plot.
The main adventure is essentially a murder mystery. Several people over the past few months have been killed leaving gruesome markings on the bodies. The situation, however, is about to get a lot more personal when a close friend of the PC's is found dead. Essentially, the PC's are going to have to find as many clues as possible and track down the group and its leaders. It becomes a race as more and more friends of the PCs die or become targets and the sooner they find the killers the less they have to worry about their friends (and the dwarfs pregnant wife).
During the investigation, the PCs will discover there are 2 people pulling the strings of the cult. The actual killer is someone whom they crossed paths with in the past and accidently made his life worse because of it. Utlimately, the killer was corrpted by a charismatic individual who exploited him when he was left in a vulnerable state after he crossed paths with the PCs in the past. The killer is responsible for the act of murdering, but there is a BBEG who is responsible for making the killer. Essentially, the PCs need to find out about the cult, stop the killer, learn there is someone else pulling the strings and then stop the mastermind.
The mastermind is where things get interesting. I was reading my old Ravenloft Van Richtens Guide to Hags and it got me thinking. There was a wives tale in the book - which the author in the end says is untrue but I decided it would make an awesome story if it was true - about how Hags have the ability to switch their unborn child with that of another pregnant mother while still in the womb via magic rituals. When the hag child is born to the human mother there is nothing amiss (with the possible exception of a mean streak as they grow older) and the child is unaware of its true heritage. It grows up like every other child and learns from its parents what is right and wrong. At around the age of 40, the hag child undergoes a transformation in which they become a hag and understand their true wicked nature.
And so the mastermind is this hag who is nearing her change (and during the adventure will undergo that process).
Ultimately, the theme of the adventure is about the duality of nature. People can be born one thing, but they can choose to be another. In the hags case, the hag will come to learn that she was born a hag (and not human) but she has spent her human years performing and perfecting evil. Which is more horrifying? That which you are or that which you choose to be?
I've set up scenes near the beginning of the adventure between a Paladin PC and his father where they discuss this theme. The paladin is a dragonborn and after researching dragonborn, I have found that it is in their nature to be honorable and proud. But the paladin has chosen to honor those traditions in service to his god and thus make his father proud of the man he chose to be. This, along with other scense I have designed will hammer home the hag change along with the you are what you are but also what you choose to be theme.
Anyways, at this point, you are probably wondering how this fits in with the succubus and the dwarf. Well, I had to design an interesting urban adventure and this is what I came up with. The pregnancy ritual with the hag ties in with a pregnant dwarf in that it is all about pregnancy. It also gets the dwarf thinking about what will happen to his child and the responsibility he has. The players know that I will advance the timeline ahead by a number of years at some point in the campaign so the dwarf may eventually see his child grown up and this adventure may have a profound impact on how he roleplays things going forward in that respect. Also the PC's are at the right level to include a succubus. They aren't very high level so this seems right. It would have been ideal to introduce her earlier but things had to develop to get to this point and I originally had no plans for this type of storyline. It just kind of fell into my lap.
Right now, I am looking at how I can apply Quickleaf's corruption phases into the adventure. One idea is to have the succubus seek attention from the dwarf by her playing up that she is a target. I have no plans of making her a target at all, but she will use that to her advantage to get the dwarf (and the rest of the PCs) to do things she wants them to do. By the end of this coming weekend I should have a better idea on what I will do.
If anyone has further ideas until then, let me know. After that I will post what my plans are.
