The Gyrm are a nomadic race that once dwelt on the surface, but were driven underground by humans who considered them impure. They are a kind-natured race, but their exile has caused many of them to refuse contact with outsiders and resent those who sent them below.
They are excellent craftsmen who create very sturdy and powerful equipment, though their designs are utilitarian.
Many of the Gyrm reside in the Doors of Pharros underground. Those we encounter have already gone hollow and stare with fixation at treasure, fire or are awaiting battle.
There is only one Gyrm that we are able to speak to in game; Lonesome Gavlan. He and his dialogue make it clear that the Gyrm had their own language. They were possibly traders, or perhaps only Gavlan was and that is why he has survived and stayed away from hollowing.
The inspiration for the Gyrm closely ties them to Dwarves in other fantasy works, as they share many traits.