Ousiders are the repulsive group antagonistic towards the Western Kingdoms and Hebrion Empire. However, they can’t just be defined as a uniform group. The reason being that the ‘Outsiders’ are formed by lots of groups who disagree with the Western Kingdoms and Hebrion Empire’s monopolizing the completion of the Shadow Worlds. Even though they have grouped up to compete against superior forces, they only happen to share similar interests and ideals. Their method and ultimate goals varied.
The Outsiders were an organization made up of many different groups that had joined forces. As they merged into one, a single pledge was made.
— The oath
The organization had been united by the same ideals . Individually, everyone had different motives. Thus, the pledge had been made. And that pledge had moulded everyone into humans that wouldn’t stop at anything in order to achieve their goals.