Were beings who either by birth or by going through a “transformation” could no longer die as they were not mortal. The Norse Gods were considered immortal due to their divinity, but they could and did die just as the rest of us. Unlike in Greek Mythology were the Gods were indeed Immortal and Lived in mout Olympus for Eveternity.
In the world of the Runes series, The Gods choose from among mortals those whom were by their standards deemed worthy, and offered them immortality so they could serve them during the duration of their lives. Only the noble, strong and most heroic were chosen for this important task, these immortals were assigned thereafter to guard, protect or assist the Gods and Valkyries as needed... In some cases, Families with long lineage of Immortals were found, their sole existance was to protect and serve the gods as well as to carry out any mission assigned by them. They served them faithfully and carried their title with pride, as it was an honor to be chosen by the Gods.