[Savage Tide spoilers!]
Well, according to a late entry in the Savage Tide adventure path, she's currently residing in a manor at the shoreline of the Styx, somewhere deep in Niflheim in Hades. Or maybe that's just a vacation getaway for her. Her current residents are some arcanaloth apprentices and some, uh, draconic guarddogs.
[End spoilers]
I like the way Iggwilv's background slowly developed over the years. When Tsojcanth first came out, all it said was that she got too arrogant with her abilities and trapped Graz'zt. After he escaped and a titanic battle ensued, Iggwilv was heard from no more. All that remained were testaments to an ambitious mage that took her abilities too far, the most significant of which was the Demonomicon of Iggwilv, containing spells specfically designed to trap and control demons.
As years went by, more background surfaced as more DnD products were released. It turns out all this time that Iuz was the child of Iggwilv and Graz'zt (which was a huge shocker to me), the result of Graz'zt dragging Iggwilv to the Abyss in a sort of love-hate-mutual fascination with evil kind of thing.
Only recently did I find out that she was once the apprentice of the archmage Zagig, and assisted him with his early experiments deep within Castle Greyhawk, before they became the Ruins. I'm not sure how credible this is, since she would have had to strike out on her own, trap Graz'zt, give birth to Iuz (before or after being dragged to the Abyss, who knows), then for Iuz to be trapped by Zagig in his dungeons until accidentally released decades later.
At least, that's how I pieced it together. According to this latest adventure, the circumstances of how she ended up in the Lower Planes is left to conjecture. If anyone else tries to add more to her background, the whole thing might collapse from contradictions!
