Anguy is a talented archer from the Dornish Marches. he is a commoner, from no privileged background.
A Game of ThronesEdit
Anguy participates in the Hand's Tourney in the archery competition, where he outshoots Ser Balon Swann and Jalabhar Xho over 100 metres. He refuses an offer to join the guard of Lord Eddard Stark, instead riding out with Lord Beric Dondarrion to bring Ser Gregor Clegane to justice. He squanders all his winnings on whores, win and other luxuries he never had whilst growing up. He presumably fought and survived the Battle at the Mummer's Ford.
A Storm of SwordsEdit
Anguy joins the Brotherhood without Banners after watching Beric be resurrected by Thoros of Myr. He abandons the Faith of the Seven, instead choosing to follow R'hllor. He was presumably knighted, as many members of the Brotherhood were.
He was wandering The Riverlands with Tom of Sevenstreams and Lem Lemoncloak when they discovered the disguised Arya Stark, accompanied by Gendry and Hot Pie. They take them on with them, until Harwin, a former Winterfell guard, identifies Arya as being a high ranked hostage.
The Brotherhood then try to track down their leaders, Beric and Thoros, who are notoriously hard to find. on their way they stop off at Stoney Sept, where Anguy takes pity on some northmen in crow cages and kills them quickly. Anguy also believes that Tom had, at some point, had a relationship with Lady Ravella Swann, the wife of the Lord of House Smallwood.
After Beric dies for a final time when reviving Catelyn Stark Anguy abandons the Brotherhood, possibly because he doesn't agree with its new, vengeful motives. He is allowed to leave, and is not alone in doing so. He presumably heads back to his home in the Dornish Marches.