Novel by David Drake. The main protagonist is Nils Hansen who is brought from his futuristic Judge Dredd like duties to a strange multiverse which mirrors the world of norse mythology in a surreal way with a very feudal and primative society that inexplicably has access to bits of high technology such as powered armor stemming from the mysterious Matrix (a sort of realm of ideals as Plato often philosophized about and some how links the nine worlds) Features an interesting pantheon of norse gods with peculiar twists. The protagonist is, of course, a master tactician in keeping with David Drake's other books.