Norse Mythology: Watches the rainbow bridge, Bifrost, for the coming of the frost giants at the Ragnarok, at which time he will sound his horn Gjallar. In the Ragnarok, he and Loki will kill each other. He never sleeps, can see in the dark, and can hear sheep wool growing. His dwelling place is Himinbjorg [heavenly mountains]. Nine sisters, signifying the waves, gave birth to him. As Rig, he begets Thrall, Carl, and Earl, representing the three classes of man: slave, freeman, and noble.
(Nicole Cherry, A list of Norse Beings, http://www.ugcs.caltech.edu/~cherryne)