Unfortunately Prince Damon wasn't able to complete the challange. After mating with one. He couldn't breed with the other donkey's.
"Hmm too bad Prince. You have failed my challange." Said Circe. "Wait please give me one more chance." Said Prince Damon.
"Sorry you know the rules. Fail, or refuse, my challange. You be my pet forever." Circe then snap her fingers.
Prince Damon fell back on four legs. Naaaaw pleaaaawse." Circe goes over to the donkeyfied prince.
She begins to scratch his chin. "Just accept your new fate my pet. This time you won't resiest me."
Prince Damon could feel his human mind fading as he starts to give into his new donkey instincts.
Eventually the changes were now over. Prince Damon was now Circe's pet donkey. Circe could see that the prince's humanity was gone.
She begins to pet him. "That's a good donkey. Were going to have so much fun together."
Circe's handmaidens then takes Circe's new pet back to the stables.