Need horror campaign idea

[The Forsaken One]

Call of Cthulhu d20 adventure "NOCTURNUM" has a great horror plot. You might want to consider picking it up. Its ideally placed in modern time but functions in Eberron quite well too.

Ive run several parts of it as one shotters and literally all of them have been a blast. This one comes highly recommended by me.

 

[Treebore]

Well, if you had 3E Ravenloft i could send you my campaign outline that I ran a few years ago (2002) that was based off of many "horror" movies, including giant irradiated (magically) ants, wasps, preying mantis, etc... as well as were creatures, vampires, flesh golems (frankenstein), possessed murdering dolls, and Anne Rice' "Servant of the Bones". It lasted until 12th level. Then I moved.

 

[Alzrius]

This isn't very immediately helpful, but if you get a chance, buy a copy of The Book of Unremitting Horror, from Pelgrane Press. It's out of print, but being reprinted later this month. It's a d20 Modern supplement, but works for d20 Fantasy just fine also. Simply put, it's a collection of truly horrific monsters, with illustrations and descriptions that will not just frighten your PCs, but actually scare your players as well.

It's also got a new feat, several artifacts, plot outlines, and an adventure at the back of the book. Seriously, if you want horror in your d20 game, I can't recommend this book enough.

 

[Desdichado]

I've had pretty good luck adopting Lovecraft stories into D&D, or a D&D-like mileu before. I ran an adventure that was loosely based on The Shadow Over Innsmouth before, and I've done one loosely based on a John Constantine: Hellblazer story before too. And I've even done one very loosely based on The Thing.

So that's my suggestion. If you need adventure seeds, scour through some horror short stories and/or movies for inspiration and adopt them. Less work for you, better chance that your "plot" will work (if your original source material did, anyway) and gets you some focus and a direction to head right away.

If you actually need "module" type set-up to make that work, though, there's also some great adventures for Call of Cthulhu that you could adapt to a D&D stile mileu easily enough.

 

[Shroomy]

The levels are a bit higher than what you are looking for, but have you checked out the Styes adventures that have recently appeared in Dungeon? "The Styes" (Issue 121, I think, 9th level) and "The Weavers" (Issue 138, 10th level) are not only some of the best adventures that have recently appeared in the magazine, but are very atmospheric, with lots of horrible stuff going on.