As the heir to the fief of Queensgrace, Dewin probably went through page and squire training in order to become a knight, as is customary for heirs of fiefdoms. He was raised in a very wealthy household, with many servants and slaves at his beck and call. It is unknown when he inherited Queensgrace, or when he married Lady Aeldra. As Count of Queensgrace, Dewin entertained very important nobles and royals, such as Baird of Conté, King Roger's younger brother.
Conspiracy of 249
Dewin was part of a conspiracy set about in 249 HE to overthrow Roger II of Conté and place Prince Baird on the throne instead. It started with the kidnapping and enslavement of the King's only son and heir, Prince Gareth. They kept the young prince hidden in the castle at Queensgrace before they realized that the Provost's Guard had sniffed him out with the help of Achoo the scent hound.
Once caught, he and his wife were executed by the Crown for their treasonous acts, along with Prince Baird, and, very uncharacteristically, Matthias Tunstall. Their lands were stripped from the family, and remained Princehold. There is however, still a village called Queensgrace by 460 HE, thus it was probably only the fiefdom that was renamed.
Count Dewin only appears in Mastiff.