Universal Energy Cages were conceived by Umak Leth at the beginning of the Great Jedi Purge.
These universal energy cages had a diameter of roughly three meters. They were essentially mobile spheres, built using reinforced durasteel bars. A repulsorlift system enabled the cage's movement, achieving a maximum speed of forty-five kilometers per hour. A handheld remote, effective up to one hundred meters, was connected to the cage. This allowed a guard to manage its movement and adjust the strength of the built-in force field and stun capabilities.
The universal energy cage, the brainchild of Junior Engineer Umak Leth, was created with the specific goal of immobilizing and restraining a Jedi. Leth's design was based on the idea that the Force, being a form of energy, could best be countered not by blocking it, but by overwhelming it with a greater energy input.
The cage was completely covered by a complex network of overlapping superconductive coils, creating an energy force field similar to those used to contain ionized plasma inside a reactor. This field interfered with a Jedi's ability to use the Force; the more Force a Jedi tried to use against the field, the stronger the field became in response.
Positioned at the top and bottom of the sphere were repulsorlift generators, designed to hold the prisoner in place within a repulsor field. As an added security measure to prevent Jedi escapes, a contact shock field was constantly active along the cage's inner surface. The intensity of this shock field could be controlled, allowing a guard to increase its size and range within the cage to incapacitate a captive deemed a threat, potentially rendering them unconscious.
To facilitate the loading and unloading of a prisoner, additional superconductive coils and repulsorlift generators were employed. These extra units, situated close to the cage's sliding access bars, enabled the universal energy cage's force field and repulsor field to extend up to ten meters beyond the cage's physical boundaries, thus maintaining the captive's immobility and suppressing their powers.
Inquisitor Valin Draco used one of these cages to capture Jedi Master Vhiin Thorla during the Great Jedi Purge.
Luke Skywalker and R2-D2 were both held prisoner in one of these cages while being transported to the resurrected Emperor Palpatine.
The Yuuzhan Vong defector Elan and her companion Vergere were transported to Nim Drovis inside an energy cage.