I think you can extrapolate a personality based on reactions and actions. It shouldn't be too difficult. Besides, you don't need an up-front personality to be a good villain. He doesn't need to be shouting exposition, or "CHAOS" every five seconds. He is meant to be more of a presence; his personality and motives can be gathered by his actions and the effect he had on the Crystal Ponies as a whole. Logic! What do they teach at these schools?