The figure of a Necromancer who finally put her soul into the sword was a woman named Aissa.
She is a beautiful woman who studies Necromancy to help Supernaturals win the war.
She was a human at first. But she felt that she was closer to the Supernatural than humans.
She always had the urge to kill humans or torture them before killing them. And that's what Supernatural does.
Aissa helps the Supernaturals in The Great Supernatural War because before humanity started the rebellion, Aissa had worked with the Vampires and used humans as material for her dark experiments.
Aissa enjoyed it all until the rebellion finally happened. And humanity has finally won the war with the power of Magic.
After that Aissa was cornered and when she was about to die, she used her remaining strength to insert her soul into one of the swords lying not far from her.
