found some info that seems to have gone unrecorded here but has been recorded on other sites and worth looking into that sheds much light on what the lady of pain is and is at least worth looking into if you have the book "Die Vecna Die! describes the Lady of Pain as a member of the Ancient Brethren, a group of omnipotent beings who predated the multiverse and know the Language Primeval, a magic greater than the gods. In the module, Vecna became a god and entered Sigil by countering the Lady's ban of all gods from the city for a time. He was able to do this because some of the Language Primeval was confided to him by the Serpent, another Ancient Brethren whose magics were as ancient and powerful as her own. After Vecna was defeated, the Lady used the Language Primeval to repair the damage he did to the multiverse by rewriting it, causing the transition from D&D 2E to 3E." source- Lady of Pain | Torment Wiki | Fandom
it would be cool if there was like some out-of-universe edition-related context/history like it said like "oh this character was introduced in 2nd edition in 'so and so book' and this and that" and maybe had some dates or stuff