Heimdall was the watchman and guardian of the gods. He could hear the grass growing in the fields and needed even less sleep than a bird. It was his duty to give warning when enemies of the gods attacked. He alerted his fellow Aesir by blowing the horn Giallarhorn, which could be heard across the world. According to the Lay of Rig, he became the father of humanity by creating the three social classes: karl, jarl and thrall.