Bound are people who can only specialize in one or two paths (Magic & Offensive), usually only things they seem to be attuned to. On a rare occasion, they can learn some talents outside of what they are attuned. Bound have been known to become Sovereigns. Also, Bound only have one life. Their spirit leaves and they are no more.
Side note: Player Characters are not and will not be Bound. Bound are only native to the current world.