Book of Mazarbul

The record of Balin's return to Moria with a group of Longbeard Dwarves in III 2989. It recounted a battle with the Orcs that inhabited the old halls of Khazad-dûm, in which Balin's Dwarves were victorious. They settled in the Twenty-first Hall, above the East-gate, and Balin himself ruled his new domain from the old Chamber of Records, also called the Chamber of Mazarbul. Over the next five years, the Dwarves seem to have settled quite successfully into their new home, exploring under the Mountains as far as the West-gate, and apparently recovering Durin's Axe and other priceless items made of mithril.

The Lordship of Balin was short-lived. Ori, who was with him in Moria, recorded in the last pages of the Book how an army of Orcs came unexpectedly out of the east, slaying Balin outside the East-gate. The Dwarves defended themselves, but they were beleaguered from the east by the Orcs, and they could not escape westward because of the mysterious Watcher in the Water. Their last stand was in Balin's Chamber of Mazarbul, where the Orcs eventually overcame and destroyed them.

The victorious Orcs seem not to have understood the significance of the Book, so that rather than carrying it off or destroying it, they left it to rot in the Chamber. There it was found twenty-four years later by the Company of the Ring, burned, slashed and blood-stained, but still readable in some parts. Gandalf passed it to Gimli to return to King Dáin, after which we hear no more about it. If Gimli was able to keep it through the battles that followed, and didn't discard it with his gear at Parth Galen, it is possible that he carried it throughout his travels in Middle-earth, returning it at last to Dáin's heir Thorin III in Erebor.