Beorn’s origins lay in the distant past, and Gandalf suspected he and his people had originally lived in the mountains until the Orcs of the Misty Mountains drove them away. He lived with his tame horses in a wooden house between the Misty Mountains and Mirkwood, to the east of the Great River of Wilderland.
Beorn named the Carrock and created the steps that led from its base to the flat top. Once Gandalf saw him as a bear sitting all alone on the top of the Carrock watching the moon sinking towards the Misty Mountains, and heard him growl in the tongue of bears "The day will come when they will perish and I shall go back!". While Gandalf knew him, Beorn did not know Gandalf; but he knew his fellow wizard: Radagast.
During the Quest of Erebor, Beorn received Gandalf, Bilbo Baggins and the thirteen Dwarves and gave the Dwarves and Bilbo help in their quest.
In the Battle of Five Armies, Beorn appeared transformed into a giant bear, rescued Thorin from the Goblins and killed their leader, Bolg.
After Thorin's burial, Beorn followed Bilbo, Gandalf and Thranduil on their way back to the west. Beorn once more hosted Bilbo and Gandalf and other Woodmen who came to celebrate Yule.
Eventually, he became a "great chief" in the Vales of Anduin, and it is said that his descendants also were skin-changers, able to take the shape of a bear. His people became known as the Beornings, and they helped defend Thranduil's kingdom of northern Mirkwood.
Beorn presumably died some time before the War of the Ring began and was succeeded by his son Grimbeorn the Old.
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