Baldur was the son of Odin and Frigg. His "wife" was Nanna Nepsdottir (Neps daughter), and their son was Forseti. They lived at a place called Breidablik. Baldur was the most beautiful of the Gods, and Snorri says he was the wisest too. There is only one story known about Baldur, the story of his death. There are many explanations about his role in Mythology. Some say he is there to show that the Gods are humanlike and also that they care about the other Gods' well being. One could also say that the death of Baldur shows that the Gods know that they can not run away from their destiny.
The story of Baldurs death:
Once Baldur had a dream that made him scared of his life. He tells the Gods about his dream, and Frigg decides to ask all things, living and dead, not to harm Baldur. This she does to every thing, except the mistletoe, which she thinks, is too young to hurt Baldur. Loki forgot to ask the mistletoe and makes an arrow from it. Loki gets Bod to shoot the arrow at Baldur, and Baldur dies instantly. Hermodur volunteers to go to Hel and get Baldur back. Hel says that this is okay if everything in the world, living or dead mourns Baldur. This seems to work, everything mourns Baldur, but on the way home he meets Thokk, a female Troll.
She says:
Thokk will cry,
dry tears,
Baldurs cremation.
Dead or alive,
I did not get Karl's son (Baldur).
Hel shall keep what she has got.
The Troll is supposed to be Loki in disguise