Thrain was born in Erebor in the year 2664 in of the Tolkien's world. Thrain's father is king of Erebor. But when the dragon Smaug attacked Erebor, Thrain and Thrain's father left Erebor. Then they went to Moria together. But in Moria the Orcs attacked the Dwarves. And in this war Thrain's father passed away. Before his father died, his father gave Erebor's map, the key and the last of the seven rings. The Thrain then went to the Misty Mountains. And Thrain fought the Orcs for 3 years and won this war. But Thrain wanted to conquer Erebor again. That's why Thrain tried to go to Erebor alone. But Thrain was captured by Sauron during the journey. And Thrain lost his mind because of tortures. Than Thrain met with Gandalf when he escape Dol Guldur. And Thrain gave Gandalf a map of Erebor and the key. But now Thrain didn't even know who he was. And Thrain passed away shortly.