Thorin looks for the Arkenstone, the most valuable object in the hoard. A raven brings the news that Dain is coming with five hundred dwarves.
Bilbo takes the Arkenstone and goes to Bombur, who is on guard during the night, and volunteers to take his watch for him. When Bombur agrees, he puts on his ring of invisibility and goes to the elves. He asks to be taken to Bard, and gives Bard the Arkenstone to use in negotiating peace with Thorin. As Bilbo leaves camp, Gandalf reappears.
Bilbo continues to use his cleverness, resorting here even to deception in order to avert the battle that is developing and allow peace to be negotiated. He takes advantage of Bombur, the foolish dwarf who fell into the enchanted stream, and uses the ring's power of invisibility to be taken to Bard. In giving Bard the Arkenstone, he takes a great risk: It is not his property; it belongs to Thorin. Bilbo also assumes that his judgment and motives are superior to those of Thorin, who is willing to go to war for the treasure in Smaug's lair.
These final chapters seem to suggest the folly of war. Bilbo's development along the journey, which he thought was in preparation for slaying a dragon, now seems to be have been for the cause of peacemaking.
sentinels soldiers charged with guarding.