Three Disgraces
The Three Disgraces were in mythology the daughters of the great God Blind Io. Their mother may have been Bissonomy, but this is not stated for certain: like other alpha-Gods in pantheons accross the Multiverse, Io may have been bang alongside the idea of an open marriage insofar as it happened to him, but just let the wife stray, or anyone look at her in a funny way...
They are named as Nudicia, Pultrichrudina, and Voluptia, names that should afford some small clues as to their nature. During the terrible passage of the Quire in the river's Old Treachery mood, Vimes is sure that part of the detritus surrounding the ship is a briefly-glimpsed marble statue. It is. One of the finest artistic representations of the trio, that adorning the Ramkins' private bridge over the river, has been destroyed along with the bridge in the passage of the surge. Never mind; there is another version in Mad Jack Ramkin's artistically important bathroom, with just enough gauze and urns to blur the line where art may become pornography...