Interesting article up on the whole Graz'zt/Iggwilv love affair.
Rule specific material is minor and can be adapted to any version of the game. I am going to use this with my 1st ed game in fact.
As can be expected I like Iggwilv. To my knowledge no one has ever penned her "biography" in full, but it would make for a good read I think. Raised by Baba Yaga, infiltrating the Circle of Eight, her years with Graz'zt as master, lover, prisoner and bitter rival. The authoring of the Demonomicon. The Rise and Fall of the Witch Queen.
Iggwilv is a great villain not because she is evil (though she is that) it is because she lack any moral compass whatsoever. If she needs a tome of magic and entire village stands between her then she had no issues burning it down to the ground. It isn't because she doesn't care, it because she has no concept that anyone other than herself matters.
I am sure she is going to play some role in my 3.x and 1st ed games.