This one is inspired by the 2006-2007 version of Hadestown, which featured Cerberus, played by Sara Grace, as the human head of security in Hadestown and Hades' main supporter.
Dog
A dog's loyalty was earned over the years, and like the one she shared her name with, Cerberus had earned her place at Hades' side. She had started like most workers, in the mines and steel mills, and soon her hard work earned a promotion to forewoman.
From there she worked her way up to head of security in Hadestown, and she intended to keep her position. Her job played to her strengths—Cerberus had an eye for detail, and when she spoke, the others listened. She prowled around the wall and its borders, making sure to feed the guard dogs, and they greeted her with nuzzles rarely afforded anyone else.
She was proud of her work, but knew her luxuries balanced on a pin. In return for Hades' food and shelter, Cerberus protected his town from intruders. Orpheus was just one of many troublemakers, and once he was found Cerberus was quick to capture him.
Hades would decide what would be done with the poet, and until then, Cerberus went back to her station to await further commands.