Mistress Gaia and her friend wanted to use this guy as an example to anyone who pissed them. The mistresses humiliated him by trampling him and caging him. He was cramped and he was in pain. They also rode him like a pony before he was taken back to the cage. While in the cage, the mistresses forced him to jerk off to their instructions while they watched and gauged whether he did the right things.
Mistress Gaia had always wanted to have a pony but she lived in the city and in an apartment so she could not have one where she lived. But she could have a human one. She turned her slave into her human pony and she enjoyed training him to be her pony within the house. He was to transport her anywhere she wanted to go within the house and when he did not meet her expectations, she whipped him.