Possible Eberron Halloween One Shot- Ideas?

[Engilbrand]

I may run a Halloween one shot for some friends. I'm trying to get some ideas. If you're wondering why I'm asking a month and a half early, the answer is that the idea recently came up and things are already percolating in my mind.

Game idea- The rogue member of House Vadalis based in the Mournland has captured a special royal members of each of the countries. The head of Thrane, the "sister" of Kaius, a child of Boranel. You get the picture. They have been take to the Mournland for some dire experiment. Maybe it's to try to extract the original king from his descendants. Maybe it's just to restart the Last War. I haven't decided.

Each of the countries comes together at Thronehold. The 5 leaders, which includes Cyre, bring one of their best agents for the mission. They are to work together, "For King and Country!" to bring back all of the missing people.

Premade characters- There are a lot of interesting things out there, and I thought that this would be a fun way to throw some representatives of the different nations together for a little conflict. Each person will be given a character sheet and a one page history/background thing. Most of the people haven't played Eberron, so this is where they'll get the fodder for in-game roleplaying. (Knowing my group, roleplay will be a focus.) They will probably be level 11 or 12.

Thrane- Human Paladin of the Silver Flame- Lawful Good- Cardinal Krozen and girl chose him personally to see to the return of Thrane's monarch. He spent most of the Last War fighting against Karrnath.

Karrnath- Warforged Revenant Assassin- Lawful Evil- He has served his country with distinction.... twice. He believes in the power of Kaius to keep his country on the right path. He believes in doing what's necessary. If he needs to torture, he will, but that doesn't mean that he goes out of his way to do it.

Aundair- Human Wizard- Good- He was famous for negating enemy spellcasters. (Don't know much about Aundair, yet.)

Cyre- Unknown (Probably a Warlord.)- (Need to evaluate later.)

Breland- Changeling Rogue- Good- Member of the Dark Lanterns- He has spent most of his life spying on the other nations.

What I'm looking for- After the initial meeting, we'll probably fast forward to entering the Mournland. I'm looking for some ideas of things to encounter. Not just obvious combat, but some of the oddities of the Mournland. I currently have the idea for them to come up a small village that seems to be going about its business, but there are no children. Ideas?

I want this to be disturbing. Roleplay and combat opportunities should come together creep the players out. Assistance?