Necromancy

Necromancy, commonly known as the Black Arts, is a sub-school of Conjuration. It focuses mainly on enslavement and utilization of involuntary souls and their bodies. It is also responsible for creating black souls gems.

Background
Necromancy isn't illegal in the Empire. Body and spirit are protected as property, and may be used only with owner's permission. Morrowind is the only province of Tamriel where necromancy is banned and forbidden. Mages may purchase corpses and souls and do with them as they see please in private. Necromancers and Vampires are widely confused in the public mind and persecuted, but in remote locations, they are free to pursue their art. Necromancy is still widely debatable across Nirn, and different cults have different standings on it. Necromancy also involves reanimating dead and the creation of black soul gems, capable of holding the souls of humanoids. The Mages Guild banned the practice of Necromancy under the rule of Hannibal Traven, which is the reason why many students left the guild. Falcar of Cheydinhal, however, still studies necromancy, without the guild's knowledge. Many necromancers strive to become Liches, but very few have the proper knowledge and skill to do so.

It is unknown whether the guild allowed necromancers back into the guild before it's collapse during the Great War in Fourth Era. As of 4E 201, the College of Winterhold allows practice of necromancy, to some degree at least. Skyrim as a whole technically permits practice of necromancy, but the people are very disapproving of it, and may even treat necromancers with hostility.