Thanks to everyone for their suggestions!
That sounds good, but sadly I'm not very familiar with Planescape or Sigil (except for a few short trips there as a player). I couldn't find any reviews online - does anyone have experience with it? I think I'll have a look at it.
Makes sense, as it was also done by Rich Baker (of RHoD fame). An interesting suggestion, albeit for a higher level group that intended.
But perhaps the precursor adventure Cormyr - Tearing of the Weave is worth looking at? Does anyone have experiences with that? It seems to have received rather positive reviews.
I've played through it once, but was a little underwhelmed in terms of roleplaying opportunities. Also, the plot seemed rather linear and the dungeon positively overcrowded. Perhaps that was due to the DM being not that great; it would seem that the interaction with the kobolds/goblins should provide some interesting situations.
Interesting. It appears to be a good campaign, but at least one of my players has the book and at least skimmed through it already (although, being a bit goth, he'd love me to DM it), plus it seems quite a bit larger in scale as I intended to commit to. I'm also not sure if my immersion-challenged players would be able to sufficiently appreciate the horror theme.
So far I've only seen horror adventures work well (in terms of immersion) with an excellent, well-prepared DM and roleplaying-oriented players. Does this one make it easy for DMs to convey the special atmosphere?