A Dwarf of Durin's Folk descended from KingNáin II, and thus closely related to the royal house of the Longbeards. He had many adventures in his long life, beginning at the age of just thirty-six, when he fought in the Battle of Azanulbizar beneath the East-gate of Moria. It was in that battle that the young Balin's father Fundin was slain.
After the battle, he followed Thráin and Thorin back to their settlements in Dunland, and soon afterwards travelled into the north with his people to find new dwellings in the Blue Mountains. The Longbeards dwelt in peace in Ered Luin for many years, but at last a longing to return to Erebor overcame KingThráin. He set out into the wild, with the brothers Balin and Dwalin among his travelling companions. After a difficult journey of four years, one rain-drenched night they camped under the trees at the edge of Mirkwood, and Thráin vanished into the darkness. It was only later discovered that he had been captured by the spies of the Necromancer.
Balin and Dwalin returned to Ered Luin with their disastrous news, and Thorin became King in his father's stead. Balin at this time was eighty-two years old, and it seems that after his perilous journey with Thráin, he was content to remain in Thorin's halls for a while. However, exactly one hundred years after Thráin had set out for Erebor, Thorin resolved to make the same journey into the east for himself, with the aid of the WizardGandalf.
So it was that Balin, with his brother Dwalin, came to be among those companions of Thorin Oakenshield who set out from the Blue Mountains and travelled with Bilbo Baggins on the Quest of Erebor. At their first meeting in Bag End Balin was described as looking extremely old (he was in fact 178 when the expedition set out), and at that first meeting, at least, he wore a hood that was coloured scarlet.
Despite his age, Balin was famously sharp-eyed, and used by the questing Dwarves as their look-out. As the eldest of the Dwarves after Thorin himself, Balin acted as lieutenant, and took charge when Thorin was absent (as for example when the companions were held by Thranduil). Along with his companions, Balin survived capture by Trolls, Goblins and Elves, a long trek through Mirkwood and a perilous encounter with the DragonSmaug. He also fought in, and lived through, the Battle of Five Armies.
Balin was always Bilbo's greatest friend among the Dwarves. Eight years after the achievement of the quest, he travelled back with Gandalf to see his friend in the Shire and tell him of events in the east. By that time, the Dwarf-kingdom of Erebor was ruled by Thorin's successor Dáin II, who had become well established as King under the Mountain.
Some decades later, Balin resolved to take on another important and difficult task: the reclamation of Moria. Though KingDáin had misgivings, he allowed the quest to go forward, and at first Balin's expedition met with success. Driving away the Orcs that they found, the Dwarves settled near the East-gate. Balin was given the title 'Lord of Moria', and his followers set about exploring their new domain. The new colony was to be short-lived: after just five years, a new force of Orcs came to reclaim Moria for themselves. There was battle in the Dimrill Dale, and Balin fell there, at the age of 231. His companions had time to make him a tomb in the Chamber of Mazarbul within Moria, before they, too, fell to the invading Orcs.