Mistress Krush had beef with her slave and she felt that the best way to deal with him was to use her riding boots to inflict a lot of pain and damage to him. He never saw it coming. He was shocked at the sudden change of things and how he was humiliated as well as made to feel a lot of pain by the mistress. He never messed up again.
Madame Marissa needed to torture this guy and she did it with her muddy boots. And to make it worse, she did it with the help of a friend. The two of them had a great time but the guy did not enjoy any of it. He had to beg them not to do that but they did not listen to him as they were having a lot of fun at his expense.
Mistress Jessica was fed up with her whiny slave and she decided to dominate him in a way that would make him change once and for all. The mistress cruelly used her riding boots to do so and she made sure that he was humiliated, dominated and in pain. He never whined again after that as he knew that the mistress would not stomach any of that nonsense from him.
When this guy missed his targets, mistress Gaia and her friend had to deal with him. They had to do it in a cruel manner so that he learned never to piss them off. They considered him lazy and lacking seriousness so they had to punish him as painfully as possible. That is why the mistresses used riding boots to trample the shit out of him. It worked and he never missed his targets gain.