Shadow

A fortress of shadow is a fortress that has all of the shadow stuck inside, and the only way to get the shadow out is to blow up the fortress so the shadows can escape. It will take a lot of power to blow up the large fortress. If you use less power, the strength of the fortress will resist the amount of force you throw at it. If you don't want the shadows to escape, the fortress will still be around to suck more shadows that come near it. The fortress is alive inside your mind; you will have to make your mind free of the fortress so the shadows can walk by themselves, without their owners controlling them.