When Forossa fell to war its citizens were scattered. Many of them became brigands and thieves, however there were a few stalwart souls who decided to live by the code of honor.
Gordin was likely one such knight who became part of the Forossa diaspora. His sword was ancient and passed down to him through generations. It closely resembles the Greatsword of Knight Artorias, which interestingly enough, Artorias wielded in his right hand, as opposed to the benefits one receives by wielding the sword with their left hand. It is in Brume Tower that Gordin's story ends, but how he died or what fate he met is unclear. He may have been one of the knights who traveled to the Iron Keep at the Old Iron King's request. Perhaps he served under the Old Iron King, or was killed by him. In any case, his sword became a treasure of Brume Tower, lost to the world outside.