Entropic Oubliette

Some beings are far too dangerous to be allowed to exist freely, beyond the grip of death with powers that can damage all of creation not bound by the laws of the World Forger as the gods are. These beings were bound into what appears as a massive armillary sphere that suspends itself in the air as the rings surrounding it ceaselessly spin drawing energy away from the being trapped within. It is said that any creature contained within an Entropic Oubliette can never again escape, though if other beings were to break the rings their power would stop being drained, and while contained they could influence the world still.

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Access/Availability

The nature of these prisons makes them very rare, most consider them a myth with even the dragons only being sure that they do exist, they do not know where they all are or how to make more of them. Many things were lost in the Dark Ages including knowledge of how to construct such prisons, though those who have made a study of such myths believe they require the help of at least one god ideally more than one and getting gods to agree can be difficult.

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Complexity

These creations are unbelievably complex, the sphere and rings are made of a hybrid of living metal and crystal, while living crystal is easy enough to find there are none alive that know how to create living metal anymore, with only a small number of divine beings who could know how to create living metal. These two components form the malleable and parasitic nature of the prisons being able to contain any creature without fail by sapping their own power to feed themselves. Combined with enchantments from beings with a highly advanced understanding of magic makes these devices a total mystery to any mortal trying to understand them, they simply shouldn't be possible. They ignore the laws of physics, and magic they absorb all forms of energy from kinetic to magical yet also hold their enchantments which include the levitation constant repairing, and nondetection abilities.

Utility

The only utility is to lock something away that cannot otherwise be destroyed, to condem it to a long slow dissipation of their power until nothing remains.