Hi,
I'm thinking about writing a fanfic, (first time for me), but I'm not quite sure were to start. I have some gist of an idea, but still trying to throw it on the wheel. Around Halloween I recalled that the Sidhe or Faery folk in stories often kidnapped people to send to the gates of hell or else they would have to sacrafice one of their own. There's the prevailing thing of Kagome being kidnapped and what not, but what if she's just a lure to get the bigger prize and there's a deadline?

Sounds interesting, but I'll give you one suggestion. Kagome and Co. are from Japan. Sidhe are Celtic in origin. It'd give the story more weight and authenticity if you used demons or faerie folk from Japanese folk lore. There are several traditional Japanese demons that'd probably suit your needs. You can find some at the Obakemono Project. But that's just a starting point. I'd also look up onryo -- they're more like vengeful spirits but they can be pretty intimidating. (The ghost in the original Japanese version of the Ring is considered an onryo, to give you an idea.)

But it's your story in the end and this is just a suggestion.

EDIT: Found a good one. The Yama-uba. She's a shape shifter that lives in the mountains. Kidnaps travelers and such, and is also blamed for missing children. Here's the wikipedia link: en.wikipedia.org/wiki/Yama-uba