Pages of Pain

Personally, my group treats 'Pages of Pain' as a book that is available within the setting (banned in sigil of course), but who's author is mostly assumed to be balmy or a knight of the post... although some - anarchists mainly - claim otherwise. Many folks have an opinion on it, one way or another, but there's no direct evidence that its accurate or not. Its just a book.

And of course, most sigilites treat the thing like its made of red hot poison

Dragon Magazine #264, and yes. The stats (by Ray and Valerie Vallese) are actually disappoing if you're looking for something true to the final game, which the Valleses hadn't seen - the stats are actually based on their novel, which was based on information they were given very early in the game's development. Anyway, Ravel Puzzlewell is presented as an standard (but crazy and mazed) night hag with no enhanced spellcasting ability, Fall-From-Grace was an ordinary (but Lawful Neutral, and a Sensate) succubus with no cleric levels, Pharod was much younger than he appeared in the game (a 14th level thief, incidently), and Morte was a 10th level bard (still a floating skull, though). Those were the only four (no Nameless One, Annah, Dak'kon, Ignus, and so on), although there was another issue covering some of Torment's new monsters. The flavor text was generally very good, as we'd expect from the authors of Faces of Sigil (which wasn't a place for amazing statistical information, either).