In Norse mythology, Heimdall is the watchman of Asgard, home of the gods. He lives in a fortress called Himinbjorg, located at the top of Bifrost, the rainbow bridge that joins the world of the gods to the lower worlds. There, he watches for any danger that might threaten the gods’ realm. He is sometimes referred to as “the shining god” or “the one with golden teeth,” and is also said to be the whitest of the gods.

Heimdall is famed in Norse stories for his devotion to duty and the keenness of his senses. He barely ever sleeps, his eyes are so sharp he can see for a hundred leagues (over 300 miles), and his hearing is so good that he can hear grass growing. As you may guess, very little trouble ever gets past him. One of his symbols is his horn, called the Gjallarhorn, which he blows to alert the other gods of Asgard to danger. The Gjallarhorn is so loud that it can be heard through all the worlds when it is sounded.

Heimdall is the son of Odin, the chief of the Norse gods. His mothers were sea spirits who appear as waves, so he is said in the myths to have had nine mothers. Some Norse poems also say that Heimdall was responsible for creating humans. He had three sons, Thrall, Carl, and Jarl, whose names also represent the three social classes in Norse culture: slaves (thralls), free farmers (carls), and warriors and nobles (jarls).

Heimdall is the special enemy of the trickster god, Loki. Their personalities are naturally opposed: Heimdall is steady and loyal, while Loki is sneaky and untrustworthy. Also, Heimdall distrusts Loki because he is part Jotun (frost giant), and the Jotuns are the enemies of Asgard. As the watchman of Asgard, Heimdall also hates it that Loki can sneak in and out of Asgard without being caught.

In one story, Loki steals a necklace called Brisingamen from Freyja, Odin’s wife and the queen of the gods. He flees in the shape of a falcon, but Heimdall follows him. Loki attempts to hide in the form of a seal, but Heimdall changes shape into a seal as well. The two of them fight, and Heimdall wins and returns Brisingamen to Freyja.

Norse mythology also tells of a terrible final battle, called Ragnarok, when Asgard will be attacked by an army of giants, monsters, and spirits of the dead, and most of the old gods will die. Loki, who has been imprisoned after one too many nasty tricks, will escape and join the attackers.

Once Ragnarok begins, the myths say, Heimdall will see the enemy army approaching Asgard and blow the Gjallarhorn one last time to warn the gods. Once the battle is joined, Heimdall will fight Loki, and they will kill each other.

Heimdall was played by Idris Elba in Marvel’s Thor movies. While the movie character was quite different from the mythological figure, they both shared the courage and loyalty that define Heimdall’s personality in the myths.