In the opening scene of Thor: Love and Thunder, Gorr finds Rapu, who was celebrating the death of the Necrosword holder. Later, Rapu disappoints Gorr and Gorr kills him.
Who was this previous holder of the Necrosword? Was any backstory given to him, or is his name even known?
In the MCU he doesn't have a name (or at least no name given in the film), but the studio responsible for his concept art dubbed him The Dark Shadow Lord
He appears to be based on the evil god Knull. Gorr inherits the necrosword from him in the comic Thor: God of Thunder #6, on which the movie is loosely based.
