Why Heimdall Blew His Horn: Tales of the Norse Gods.

In Norse* mythology, the god Heimdall stood guard over Asgard, the home of the gods. He lived near Bifrost, the rainbow bridge that connected Asgard to the world of humans and from there kept watch for the approach of the giants, who were the enemies of the gods. Heimdall had incredibly sharp senses that allowed him to see great distances even at night and to hear sounds as soft as wool growing on sheep or grass growing. Furthermore, he needed little sleep. According to legend, Heimdall would one day call the other gods to Ragnarok, the final battle that would result in the destruction of gods and humans. When the giants drew near to Asgard, Heimdall would summon the gods by blowing his horn.