Mason is a werewolf of the Berradin Pack. He is over 700 years old. He was leading the pack on a full moon hunt the night of the attack on the werewolf village that left Hamish's first wife and all the children of the village dead.
Father to Hamish Berrin
Father to Corran Berrin
Mason was born in the Highlands of Scotland and lived there for hundreds of years. He chose about 15 years ago to start looking like he was aging.
In A Wolf's Song, we meet Mason when Desiree first encounters him. He aids her a way that gives us clues as to his true nature. In A Gargoyle's MIght, we discover that true nature more closely for ourselves.