Baranthor is a Great Eagle of the Misty Mountains. He accompanied Lord Gwaihir and Armenel on their trek to the Ettenmoors, on their search for Bargrisar, the stone giant. Bargrisar prieviously attacked many of the Eagle airies, which houses fledgelings (baby Great Eagles). Bargrisar fled before the Eagles could bring him to justice, and so they searched for him at the Ettenmoors. Baranthor, Armenel and Gwaihir arrived on the scene of Bargrisar's death to find the Three Companions (Eradan. Andriel amd Farin) and Beleram standing victorious. The praised the four for ending Bargrisar. As Lord Gwairhir was giving leave to Beleram for him to accompany the Three Companions, Barnthor jumped on the chance, pleading for Gwaihir to allow him to also accompany the Three Companions. Armenel also wanted to go. Gwaihir, with his great wisdom, estimated the fates of "thethree who cleave the air" and "the three who walk the ground" were intwined together, and so let all three Great Eagles go.

Baranthor himself is eager to prove that he is worthy of an Eagle, and take after his father. His father fought in the Battle of the Five Armies. Baranthor is eager to go to battle and make something of himself, and says he fears almost no oponent, be it ocr or troll. Beleram is often his mentor, teaching many hunting and fighting tactics. Beleram tought himo "pluck the hairs of a wolf" and snatch a sheep off the ground with hast.

Baranthor and the other Eagles accompanied the Three Companions to Rivendell, and then to Mount Gundabad, where they distracted the Fell Beasts and then saved the Three Companions from the collapsing roof. At Bruni and Nordri's command they traveled many leages over the Misty Mountains and to the secret hold of Nordinbad. From there, they travelled to Mirkwood in search of Radagast. When they learned of Urghost's location, they carried the Three Companions there, but layed low in fear of the dragon. But they had to hurry back to Nordinbad, where a siege was being laid against it. After they set the Three Companions down, they soared off to destroy the siege machines that were causing great damage. But as a vanguard of trolls assaulted the gate, Beleram ordered to swop in and attack them, but sadly, a missle launched from a siege machine flew into the air and exploded, instantly killing Baranthor and Armenel, and knocking Beleram from the air. Baranthor died at the Siege of Nordinbad.