Containment field device

Energy Prison
The 'Energy Prison' is only ever seen in Halo Wars in one or two of the cinematic, presumably Forerunner], where [[Professor Anders is being held. It is comprised of two rings - probably not static. They make touchable energy similar too that in an Energy Bridge. They encircle the prisoner, presumably the energy covers most of the body, and forms around the prisoner. This would explain why Professor Anders couldn't move more then a couple of centimetres, and why she fell down when it was de-activated.