While I am sure that Jason Am(brus)'s suggestion will prove fruitful, I think that a literary text, or a few of them, might be a better source to try out (you sort of get a total package, a better "feel", maybe, than a historical text... Though I agree with the Wikipedia...)
Now, what would I suggest as ressources?... (For that matter, where the hell does my knowledge come from? lol!)
Shakespeare - You might want to try out something like Romeo and Juliette. It's kind of cheezy, in that we all know it too well, but the feel of warring families, crimes of passion, etc (plus the great names! Tybalt!!!) make for great material. Other choices I would recomend from "the Bard": Merchant of Venice (you can check out the movie with Pacino - it's pretty good!)... mnay of them are good for this, I feel...
John Webster's "Dutchess of Malfi" - a young widow marries against the wishes of her elder brothers... vengeance and violence ensues. (Also, there is a short bit about one of the characters being a lycanthrope.
)
hmmm... I know there's a lot more out there, but it's not coming to mind right now... i think the feel for Invidia is for individual passions vs. political maneuvering. Small, subjective passions with larger consequences is best. (or has proven the best for us...)
Anyways, as a bonus, all of this stuff is available for free at project gutenburg:
http://www.gutenberg.org/catalog/Barbarossa Vineyards - Fine Brandies. The choice of true connaisseurs. (Located an hour's ride outside of Karina.)
A loose collection of writings about our (sometimes) ongoing campaign. http://ravenloft.inoveryourhead.net/
