- "Ulf is demanding blood money, which Shagga and Gunthor refuse to pay."
- ―Tyrion Lannister
Gunthor is a member of the Stone Crows, one of the Hill tribes of the Mountains of the Moon recruited by Tyrion Lannister to fight for him in the initial stages of the War of the Five Kings in exchange for gold, weaponry and armor the hill tribes could employ against House Arryn.
Tyrion reports to his father and his uncle that a Moon Brother stabbed a Stone Crow over a sausage; in retaliation, three Stone Crows seized the Moon brother and opened his throat; Ulf of the Moon Brothers demands blood money, but Shagga and Gunthor refuse to pay.
In the books
In the A Song of Ice and Fire novels, Gunthor son of Gurn is the chief of the Stone Crows. He is described as a thin man in a horned helmet, armed with a long knife.
Gunthor, along with Shagga son of Dolf and at least ten more of his clan, encounter Tyrion and Bronn in the Mountains of the Moon. In the novel, Gunthor is the first to introduce himself to Tyrion by saying Shagga's TV-series line: "When you meet your gods, say it was Gunthor son of Gurn of the Stone Crows who sent you to them". When Tyrion teases the clansmen for their cowardice, Shagga becomes enraged and threatens Tyrion, but Gunthor silences him and lets Tyrion speak.
Gunthor is not among the clansmen who follow Tyrion to the Lannister camp, and subsequently participate the battle of the Green Fork; he stays behind at the mountains to rally the other hill tribes.
In "A Storm of Swords", when the Hound and Arya arrive at a small village, on their way to the Vale, the village elder warns them that it is very dangerous to pass the Eastern Road these days, because the clans have steel now, good swords and mail hauberks; he tells them that half a year ago the Stone Crows, led by Gunthor, raided a nearby village, took every woman and every scrap of grain, and killed half the men.
Gunthor is not mentioned in the following novels. For unknown reason, it is not him but Shagga who is listed in appendices of "A Feast for Crows" and "A Dance with Dragons" as the chief of the Stone Crows.