According to the genealogy on p. xv of Hrolf Kraki's Saga by Poul Anderson, King Helgi begot Yrsa on Queen Olof and Skuld on the Elven Woman. This second, mysterious woman shows up on pp. 88-92. She and three men in rainbow cloaks and flickering boots sit on shimmering elven horses, "...changeable as waterfalls...," which speed away "[s]wifter than flesh..." (p. 92) She claims descent from Ran and says that her child by Helgi "...must be born undersea..." (p. 90)
I mention this because these elves are the first supernatural beings to come onstage during the novel. Others will follow. There is an important difference between novels in which gods are believed to exist and those in which they are seen to exist. There is a further distinction to be made between novels in which the human characters experience the effects of the gods' activities and those in which the gods themselves come onstage as characters. When, on p. 189, King Holf meets a tall man with a broad-brimmed hat, a shadowed face, a long gray beard, a blue cloak and a spear and who, on p. 194, has two ravens flying above, we recognize a divine character whom we have already met elsewhere.