Mistress Medea was pissed at how her supervisor picked on her. She did everything right but he never failed to get a reason to humiliate her and find fault in her. She was fed up and she was ready to lose her job. But before she did, she hunted him down and she fucked him in the ass with a strapon to make him realize that she was not going to accept such treatment again.
This mistress wanted this slave to be punished and she did not bother to invite someone else to do it. She knew what was needed and how she wanted him to behave going forward so she used her smothering fetish to dominate him. He was in pain and he was humiliated and that is what pushed him to agree to do things the way the mistress wanted them to be done.
Mistress Medea knew this guy was not gullible but it was her intention to make him one. And she did it by teasing him with her hot body and the way she was seductively dressed. He could not resist her and that is how he fell for her trap. She managed to make him humiliate himself for her sake and she had a great time watching him do it without any clue that he was not turning her on but rather humiliating himself.