Volf Volfssonssonssonsson was a Hublandish warrior of the Vasung tribe who was slain in an inter-tribal squabble with the Bergund tribe- along with a lot of others. However, as the rest of the slain were being carted off by Valkyries to feast in Valhalla, his soul was still tied to his body. It took a very nervous sixteen-year-old Susan Sto Helit to sever the two, with frantic instructions from the Death of Rats during the events of Soul Music.
Death was off on one of his fancies and, as she'd turned sixteen, the nature of things decided she was the one to fill the vacuum. Which was stupid and illogical, and Miss Butts would have had something very sharp to say about it had she found out.