The Myth of Baldar is one of the most well known myths in the Norse tradition and plays such a key role in Norse Heathenism
Balda was the Son of Odin, and was the god of sunshine and summer, and was seen as being perhaps one of the most pure and good of the gods.
Odin had foreseen that Baldr's life was in grave jeopardy, but did not know the exact details. Therefore, Frigga, his wife and the mother of Baldr, went forth and bade every living thing on earth swear not to hurt him. She extracted her promise from everything except the mistletoe, which she deemed too young and tender to make a binding vow. When Loki discovered that the mistletoe had been excluded, he made an arrow out of it's boughs. As the gods were making merry with Baldr, tossing all manner of things at him that they knew could not harm him, old blind Hoðr stood alone. Loki approached and asked why he did not honor his brother by attempting to harm him. Hoðr replied that he had neither a weapon to cast nor the sight to cast it. Loki furnished him both, and Baldr fell dead when struck with the mistletoe arrow. Hoðr, realizing too late what he had done, fled. This proved his undoing, as it made the act a murder rather than an accident, and a murder demands justice. Needless to say, Loki took off as well.
Baldr's soul immediately departed for Hel, and the gods dispatched Hermóð, the messenger of the gods and a son of Odin to visit the goddess Hel, Queen of the Underworld, and demand to make ransom for Baldr. As Hermóð headed for Hel, Vali, a son of Odin by the giantess Rinda from the Western Mountains avenged Baldr by hunting down and killing Hoðr. Vali was but one day old, and had neither washed nor cut his hair when he accomplished this deed. Baldr's funeral was held in Asgard with much reverence. When Nanna saw her beloved husband's body lying in his ship, ready to be burned, she died of a broken heart, and so joined him in death. Before putting the torch to the pyre, Odin leaned over the body and whispered something in Baldr's ear. No one knows what Odin said to his dead son in that hour, nor shall anyone save Odin ever know for sure. This had become, by the Viking Age, a common expression for the unknowable.
Hermóð reached Hel and the ransom that was demanded was that every living thing should weep for Baldr, and that if a single thing did not, then he would remain in her keeping until Ragnarok (the "End of the World"), when he will return to live in Valhalla once more.
Hermóð returned to Asgard with the ransom demand, and the gods scattered across Midgard asking every living thing to weep for Baldr. Soon was the Earth awash in the tears of living beings for the passing of Baldr. But deep in a cave the gods came upon the Hag of Ironwood, who, unbeknownst to them, was Loki in disguise. She refused to weep, thus was Baldr condemned to remain in Hel until Ragnarok.
After Loki had the utter gall to return to Asgard for a feast and brag of his misdeed, the gods hunted him down. They bound him to a rock, using the entrails of his son as the binding. A snake was placed over his head, which drips venom. His (remarkably) faithful wife Sigyn stayed with her husband, holding a bowl to catch the dropping poison and relieve some of his torment. But when the bowl fills, and Sigyn must leave to empty it, some of the venom falls on Loki's face. His writhing in agony at such times is said to be the source of earthquakes
http://www.haxton.org/Baldr.htm