Orcrist
Orcrist, the Goblin-cleaver, was the famed sword used by the legendary Thorin Oakenshield during the Quest of Erebor. Thorin used this sword for much of the journey east with his thirteen companions and the wizard Gandalf, until it was confiscated by the elves of the Woodland Realm. It was Thranduil, King of the Wood-elves of Mirkwood who laid the sword upon Thorin's Tomb following the Battle of Five Armies, and ever would it remain there to glow when the enemies of the Lonely Mountain were near.
Orcrist was forged long ago in the First Age in Gondolin, by the Noldor elves who had dwelled there. It had slain hundreds of goblins in it's time, so much so that the creatures came to fear it, calling it the "Biter". Like Glamdring and Sting, Orcrist was adorned with ancient runes, and glowed brightly whenever orcs were close. How it came into the possession of the hoard of Bert, Tom and William in the Trollshaws is beyond anyone's guess, except that perhaps they were taken from other hoards, or it's last possessors were waylaid on by the trio.
The Sword still rests today on Thorin's Tomb in Mazal Akrâz, the Chamber of Glory, although it takes no direct part in the storyline (though it can be spotted in the instance below).
Quest Involvement
The Black Book of Mordor: