I'm planning on creating a magical barrier at the entrance to level 2 which can only be disabled with DC 30 Arcana (which puts it out of their reach nicely until level 2 and even then they have to roll a 20... and any failure will alarm the hobgoblins). If they talk to Keegan, he'll mention something about seeing a female elf coming through the ruins (I'm allowing Keegan to roam the first level except the caves... basically he haunts his keep). If they fight him, he'll have some sort of more cryptic dying-breath message.
The barrier can also be lowered by speaking the correct pass-phrase, which is going to the name of the illegitimate daughter of N & Lord Paedrig (whose wife supposedly died in childbirth). The relationship between N & P is secret, and everyone assumes the daughter is by his late wife, since she's the right age, and as a young half-elf, her features aren't prominent yet.
Balgron the Fat will probably have a clue that says something like "If you need to come down for any reason, she can get you in."
The idea with all this is that if they go back to town, hopefully they'll know (or find out with some skill checks) that N is responsible for raising undead (the townspeople haven't quite put two and two together) in the graveyard. (She setup the ritual earlier, triggered it, and is hiding, watching to make sure nothing goes wrong, but she's well-hidden, so no one ordinary will possibly see her.) Their job will be to call her out on it and convince Lord Paedrig that she really is responsible (skill challenge). Any hostile act toward her will turn into a fight against both of them and the undead (the undead will not attack her but will attack him if he's closer than a PC). If they're about to kill her, she'll teleport away to harass them later in area 18 or 19. If they WIN the skill challenge like they're supposed to, P locks her up (she escapes sometime after the PCs leave town again, or as soon as they try to interrogate her--she still has a teleport power
) and invites them back to his manor where he shows them all her belongings, including a note from Kalarel that either hints strongly at or flat-out says the password.
Assuming they GET the password, the hobgoblins assume they're authorized visitors and give them directions which a warning that if they stray from the directions they've been given, they will be treated as intruders. This gives them a way to bypass some possibly repetitive fights, and they'll earn XP as if they had defeated them (but no additional XP if they actually go fight! no double-dipping!).
From there things proceed as normal, except for a random chance that N shows up in a fight later. Maybe her teleport power is daily.
Maybe she's having a relationship with Kalarel too. Maybe he'll kill her for failing him. Who knows.
