Iron Imprisoner

The Iron Prisoner (アイアンプリズナー) is an Unversed that is found in Kingdom Hearts Birth by Sleep. Although it is a boss, it only appears at Mirage Arena. When it is first fought, it is chained and imprisoned in a gibbet, but it gradually releases itself over the course of its battles. The four forms it takes are known as "Iron Prisoner I", "Iron Prisoner II", "Iron Prisoner III", and "Iron Prisoner IV".