Heimdall is known as a god of light, and is the keeper of the Bifrost Bridge, which serves as the path between Asgard and Midgard in Norse mythology. He is the guardian of the gods, and when the world ends at Ragnarok, Heimdall will sound a magical horn to alert everyone. Heimdall is ever-vigilant, and is destined to be the last to fall at Ragnarok.
Heimdall is a son of Odin, although in some tales he is described as a foster son. He is known to be the son of "nine mothers," and his birth is associated with the crashing of waves upon the shore. In some folklore, waves strike in sets of nine, and the final of these is the ram, which is Heimdall.
He is known to be very wise, and appears in several of the Norse sagas in the role of protector. He figures prominently in tales in which Thor's hammer, Mjolnir, is stolen by the Frost Gods, and in another story about Freyja's necklace, Brisingamen, taken by the mischievous Loki. In both of these, Heimdall is the one who recovers the missing items. Despite his dedication to his job, Heimdall is known to occasionally disguise himself so he can sneak off-duty and have all kinds of adventures.