The Codex of the Necromagi
Little is known of the original Necromagi. Only legends remain, passed from father to son among the illiterate peoples in the forgotten places of the world.
Among the hill people of the Fire Peaks stories are told of a powerful arch-magi who lived in a tower that stood a thousand feet over the tallest mountain. The Magi was mighty in all things arcane and good to the hill people who struggled to live in a harsh land. He would divert rivers to give towns water and smash hillsides to create rocks for construction.
Then a dark plague swept over the land and many died. The arch-magi lost his wife and his daughter to the illness. In his rage he opened a portal to the realm of the dead and challenged the Raven Queen, demanding she return his wife and daughter. He was defeated, but he learned from his failure and survived his battle with a goddess.
When he tried again he was wiser. He prepared a ritual to find his wife in the shadow realm and went to her first, binding her soul to his so they would be stronger when they went to the Raven Queen’s court to demand the return of their daughter. The Arch-Magi never returned from the land of shadow. But his ritual remained in his tower, lost for a thousand years.
It was the Tyxians who rediscovered the ritual. By combining the soul of a dead wizard with the soul of a live wizard they created battle magi that were all but unstopable in war. The costs of such power are considerable. The ritual will not work on one already dead, you must kill a powerful wizard as part of the ritual. The body of the Necromagi wastes away over the years as the power is too great for mortal form.