Lily's madness was due to her use of the mirrors
- Like Voldemort's Horcruxes, Lily Weatherwax's power amplification of the mirrors sapped her sanity. Not to say that she was lovely before, of course. (Seeing as, among other things, her briefly-mentioned backstory hints that she was The Vamp who, unlike Nanny Ogg, used magic for her canoodling). But while the several passages mentioning the dangers of using two mirrors foreshadow her Karmic Not-Quite-Death, they also suggest spiritual mutilation that was never expressly elaborated on. This mutilation took away all her humanity, leaving only equal parts Tautological Templar and Super Villain.
There's a million billion images, but only one soul to go around.
- I believe this may be canon. Agnes's brief encounter with the dance room leaves her horrified in Maskerade. She could feel herself being pulled out of herself.