Secrets. Some are best hidden from the world and from other people. Although, the more secrets that build up, the angrier a person may get.

Your species has become extinct years ago. You spend your time alone, looking for something interesting, anything will do. You have traveled all over the world meeting many types of people, and now your in England. As you traveled around you "accidentally" run into the phantomhive house hold. That is how your life got a little bit more interesting and annoying. You remind your self though "don't fall for the snake that tells lies" you won't let HIM trick you. (I don't own black butler)