Nokris was Weak in strength unlike his brother Crota, yet Strong in mind. So he used Magic, Necromancy, Alchemy like the Wizards do. Nokris though was Male, so he looked different he chose to be male as he had a choice on what and who he wanted to be and do. It's set up as follows by Present day Hive: Worm gods Oryx Savaithun/Xivu Arath Crota/Nokris/Daughters Of Oryx/Dull incaru. Children of the Children (Hash) Brood Queen's/Ascendant Champions Knights (Male) Wizards (Female) Acolytes Thrall/Oger Larva The Thralls and Acolytes have no Sex(Biologically) Knights and Wizards both Control a Set amount of lesser Hive, Acoylets Control a Set amount of Thralls. If a Knight dies, an Acolyte Takes the Knights place. Same for the wizard, same for Thralls. Once they become a Knight there then a Male, and wizard, Female. It continues up until Ascendant Champion and Brood Queen. As to be a child or and a Ascendant Hive you have to be chosen by either the Children of the Children or by Savaithun/Xivu Arath themselves. Crota chose Hash as she was as big as an oger and stronger, as a Thrall, yet she liked magic and alchemy more than brute strength like her father. Edit: on the "Witch", I believe Savaithun is the only one with that title as she was the First.