For many generations they were necromancers who sought out control of Austermeere through increasingly gelatinous armies of the dead. But after the Schism, in which sorcerers were brought under the heel of government regulations, the Thorn family evolved to be more peaceful and academic in necromancy, rather than practical. I liked them very much.
I admit to some surprise that demons are mortal, in your world. It is very different to what I am used to.