True, it is easy to bind. But is it worth it? First, its voice cannot be turned off, I'll have to specify that. Second, it's gaze is still active, but anything binding itself to something this cursed is bound to suffer a severe if not fatal consequence. Even if they managed to survive, using powerful magic to hold the bond but suppress the curse that comes with it, the creature is shrouded in mystery. This gives DMs a lot of elbow grease for even worse unexpected consequences. In mythology, in one part of the world, it is considered an aspect of the devil itself. I never defined its final state on this, leaving it open on purpose. Therefore, by binding an Akuma to serve, you could accidentally end up getting the attention of all Akuma's (happens much easier since there are not a lot of them), which are something like Avatars, but with their own odd system, or possibly offending the oldest of their kind, which would be dangerous considering a fledging of its kind starts out with 22 DC (as they claim the ladder, it doesn't take too long before they are too powerful for any binding). They may have their own culture, laws, customs, and all sorts of strange things that are beyond anyone's ability to scrutinize because they are all spread out over the universe operating alone at all times. I'll admit its not done yet, there are a few things to go over, it should be done soon. I'd be perfectly fine with players taking control of one, and fast learning never to ever try doing so again. Its a great way to lose a character real fast... remember these things trap souls, drag souls to hell, and that is only for leisure and fun, a hobby on the side of whatever bizarre schemes and conspiracies they involve themselves with.