Creative Bugs?

Similar holding cells were rather common across the Eternal Empire of the Asurya, especially when it came to the prisons that were supposed to hold species like Arachnids or Illithids, as both of them were hard to contain.

It wasn't just about the containment itself; one needed to contain them safely without any possibility of them breaking free from their imprisonment, harming the personnel, or creating more problems. 

Arcturus knew that the Empire had even more advanced and exotic prisons that were apparently capable of securing and holding even those at the Beyonder Realm, but only those of the weaker grade.

Anything stronger would be impossible to imprison by the Empire.

In the end, the Empire was rahter young among the High-Level factions, and their foundation wasn't that deep compared to the other High-Level Star Nations and High-Level Civilizations across the Cosmos.