Dwarf and King Thráin II of Durin’s Folk, b.TA 2644, d. TA 2850. Son of Thrór and father of Thorin Oakenshield, Frerin and Dís. Thráin II succeeded as King in Exile after the murder of Thrór in TA 2790.

Thráin was raised in the dwarf realm of Erebor, which his father Thrór had re-established, under the mountain, returning there with the Arkenstone the glittering symbol of their House. They prospered and had good trade relations with the Men of Dale. But in TA 2770, when the dragon Smaug in jealous rage, descended upon the mountain in flame and terror, Thráin and his young family, were driven into exile along with his father Thrór.

The murder of Thrór in TA 2790 led to the War of the Dwarves and Orcs. Thráin led the Dwarves at the Battle of Azanulbizar in TA 2799 where he was gravely wounded, and lost an eye. After the battle Thráin returned over the Redhorn Pass to Dunland and from thence wandered North with his family and other kin until they settled in the northern Ered Luin beyond the Gulf of Lhun.

Thráin was the last of the Dwarf kings to possess one of the Seven Rings. In TA 2841 he became restless and, unable to live any longer within the Dwarf dwellings of the Blue Mountains. He left the Ered Luin and wandered far abroad with only a few chosen companions. He was captured in Mirkwood by agents of Sauron (the Necromancer) and imprisoned in Dol Guldur. Sauron took the Ring from him and for five years Thráin was tortured but managed to keep secret the existence of the Side-Door of Erebor, his map and the key.

In TA 2850, Gandalf the Grey, infiltrated the caverns of Dol Guldur, and found Thráin there. In The Hobbit Gandalf explains that Thrain was old and sick and close to death. He knew not his own name nor the name of his son, but entrusted the map and key to Gandalf, dying soon afterwards. Later, when Gandalf realised who the prisoner had been, he initiatied the Quest of Erebor and passed the map and key to Thráin's son Thorin Oakenshield.

Note: Additional information from Cirdaneth
Encyclopedia entry originally written by atalante_star