Mika grabbed the indicated supplies, but he knew he couldn't use them on the centaur. The fellow was kind and considerate, and deserved better. After looking to make sure Robin had left the stable, he put the supplies aside and went into the stall.
"Sir! You have to get out of here! My master is an evil man who wants me to turn you into a normal horse. And if I don't do it, he has a powerful magic object that he can use to transform you instantly into anything!"
The centaur frowned at first, but then nodded. "I have heard of such things. Thank you for warning me, boy. Come with me! We can slip out and find help at another town. I have many friends who would be willing to come back and destroy this place."
Mika thought about his options. If he left, he might never be able to change back to his old self. But if he stayed after letting the centaur go there was no telling what Robin would do to him. "Yes, I'll go with you!"
He gathered a few things from his own stall, then came back and climbed up on the centaur's back. The centaur headed for the doors, which were open enough for them to pass through. "Once we get out of here we can..." The centaur stopped suddenly, and Mika saw with dread that Robin was standing in the courtyard outside, a grim smile on his face.
Mika was suddenly falling as the centaur seemed to come apart with a chorus of strange squawks and clucks. Mika hit the ground, his fall cushioned by a feathery lump that cracked under him, while other forms fluttered and tumbled around him. Crying out, he batted at the shapes until he realized he was surrounded by a large flock of... chickens?
He scrambled up, finding a dead hen underneath him, crushed to death. The birds scurried around in apparent confusion before settling down to peck at the ground. They were all identical, and even moved almost in unison. It took him a moment before he realized what had happened. "You turned him into chickens!"
Robin nodded. "A nice flock. We have been running low, and I expect to use quite a few for dinners. Each one has a fraction of the centaur's mind, enough to be a chicken but nothing else."
"But..." Mika flushed and felt sick. "He was a nice person! I could have made him into a fine stallion, at least."
"Yes, you could have. And he would have enjoyed a long and healthy life as a pampered stud." Robin shrugged. "But instead of giving him that life, you betrayed me. Now he will exist split into two dozen existences, all of which will meet quick and brutal ends when I chop off their heads and cook them."
"Are you going to kill me now?" Mika shivered miserably. He had failed the centaur and doomed himself.
"Oh, no!" Robin grinned. "This was just your first mistake. And a good lesson. The next time I give you an order, you have some idea of what will happen if you disobey. The ones you try to help will end up far worse off." Then he chuckled and turned to go back to the Inn. "Sleep well, boy!"
Mika stood among the chickens for a long time before he went back to the stable and huddled in the corner of his stall for the rest of the night.