Mistress Anastasia noticed that she had a slave who was prone to making errors and she knew one day he would piss her off to the extent that she would punish him. So she chose to scare him instead of having to wait for him piss her off and get a real punishment. So she threatened him and scared him with her sharp teeth and he was scared of her and he tried his best not to mess with her.
Mistress Anastasia was not ok with how her ex had dumped her. She felt that she deserved better and so she had to dominate her ex and teach him never to do that to someone else. That is why she smothered him with her bbw ass and she forced him to endure the pain and humiliation that came with it. He learned to break up with people in a civilized manner.