Who is Mr. Hyde?

After reading the first four chapters in this book, we still don't now much about Mr. Hyde. Not many people have seen them and if they have, their descriptions of him are all very different. They do have one thing in common though and that is that they all describe him as being "deformed." Whether this means an actual body deformity, or a deformity of the mind, one can't be sure. Whenever Mr. Hyde is brought up in these first few chapters, there is always an air of mystery about him and also a sense of darkness. When his house was being described from the outside, it was said to be dirty and neglected. When the murder of Sir Danvers Carew was taking place, it was described as very aggressive and he was said to be a "madman." The settings in which he is involved are also creepy. They talk about him in the dissecting room and a laboratory, and the weather tends to be foggy or dark. The way he is portrayed so far in the book makes people, especially Mr. Utterson, skeptical about his intentions. However, Dr. Jekyll seems to take a great interest in him and actually seems to like him. So the question is; Who is Mr. Hyde?