Ser Aenys Frey is an anointed knight of House Frey, and the third son of Lord Walder Frey. He is a sly man who serves as a commander of Frey forces under Roose Bolton in both The Riverlands and The North. He dies outside Winterfell after Roose puts him in charge of the Frey vanguard.
Aenys has been sent north with his brother Hosteen frey to command the frey troops assisting Roose in securing the North. After people start to die in Winterfell he accuses Theon Greyjoy, but Lady Barbarey Dustin proves him wrong.