Beauty is the winged horse ridden throughout most of Dark Lord of Derkholm by wizard Derk, both as himself, and later in his role as Dark Lord.
Beauty is part of a breeding program Derk has been running to create a beautiful, intelligent flying race of horses who will be able to take to the air and save themselves during the mayhem and general danger of the annual Pilgrim Parties. Beaufy is fairly intelligent, but has trouble talking intelligibly. Her foal Pretty, on the other hand, does not.
Beauty is a devoted mother to Pretty, and her only real flaw is that if the doesn't know where he is, she gets anxious and tends to go off looking for him, regardless of her wizard's plans and needs for that moment.