Before Mike's consciousness faded away he found the willpower to speak up, "Wait, this isn't what I wanted."
The wizard halted, "You agreed to be his mount on this quest."
Mike said, "But I want to keep my humanity. Don't replace my mind with that of a horse."
The wizard said, "For you to be an effective mount, you have to have experience and training. The only way to give you that instantly is to give you the mind of a horse."
Mike said, "Okay, but do you have to replace my human mind for the next five years. Isn't there a way that both minds can be in my body?"
The wizard said, "Well yes, it's a little unusual but it can be done. It might even be advantageous. Aaron can have a horse when he needs a horse and a companion when he needs a companion."
The wizard waved his hand and spoke some more gibberish. Mike felt more comfortable but Aaron protested.
"Are you going to let him stay a centaur" Aaron asked, "He won't be much use as a warhorse like this."
The wizard said, "Your right but let's find a compromise. Mike, would you be willing to be transformed further into a warhorse?"
"As long as I can keep a bit of my humanity." Mike said.
The wizard waved his hand again and Mike's human parts became bigger and tougher like a warrior but they also became more blended with his horse side. For example, his hair changed into a main that flowed down his back and his jaw elongated to be more like a muzzle. His torso shrank somewhat as well so that he was still a centaur but he was now closer to 75% equine, 25% human.
The wizard asked, "Is this acceptable to you?"
Mike admired his now more powerful arms and said, "Oh yes. This is wonderful." Then Mike turned to Aaron and said, "So master, tell me more about this quest you want to go on."