A sword forged in the First Age by the elves of Gondolin.

In The Hobbit, Orcrist was found by Thorin Oakenshield and his companions, on their Quest of Erebor in TA 2941. Along with Glamdring and the knife later known as Sting, it had lain long in a troll-hoard but how it had come there from Gondolin was not known.

Elrond identified Orcrist from the runes upon it and translated the Sindarin name as Goblin-cleaver. Used in the Goblin Wars of the First Age, it had the virtue of glowing blue when Orcs were nearby. Certainly the goblins, (Orcs), of the Misty Mountains recognised Orcrist as the legendary Biter that did them much damage in Ages past. Elrond surmised that it had been plundered many times before it came to the troll-hoard. Who wielded it and how it was borne out of the ruins of Gondolin in FA 510 is a mystery.

Thorin Oakenshield bore Orcrist for only a short time before it was taken from him in captivity by the Elves of Mirkwood. When Thorin was slain in the Battle of Five Armies he was buried beneath Mount Erebor with the Arkenstone upon his breast, and Thranduil, the Elvenking returned Orcrist to him, laying it in sorrow upon his tomb. There, so the old songs tell, it still glowed blue if enemies approached the Lonely Mountain.

Note:Additional Information from Cirdaneth
Encyclopedia entry originally written by Ainulindale