The legend goes that the Great Hyne created people. The sorceresses were given a fragment of Hyne's power. It's hard to determine how many sorceresses exist today, for many keep their powers concealed. However, it is believed that they avoid spreading their power too thin.

Basically they are women with the power to use magic naturally without having to use GF's like the rest of us. And 9 times out of 10, they get corrupted with that power.