Everybody needs to find their purpose in life and this slave exists only as the personal anal whore to his Mistress.
Some slaves undergo rigorous slut training so that they can be whored out to earn money for their owners, but this slut is reserved for her exclusive use. This is a high privilege which is why the requirements for such a position are so high.
She only keeps him around to serve as her fuck-puppet which means he must be ready to take her cock morning, noon or night. He serves no other purpose and has surrendered all control to her.
This is all about being available so that his Mistress can enjoy nice long hard fuck sessions, making sure he understands that he is completely owned by her cock!
Occasionally he may be given some kind of small reward, such as her cock going ass to mouth so that he can taste his own juices!
