A Prison Pod is a weapon frequiently used by the robots during the Golden City (Era), it was able to contain and drain any information out of a captive human located in the pod. In one instance Ha-Ya-To was captured and rescued from one on the back of a Shadow Crawler by Hitomi.
The sets come with skeleton prisonners within the pods, demonstrating that draining information often results in death and skeletonification. This is pretty dark for a toy series designed for children. A more kid-friendly option would be to assume the prisonners are rendered transparant as if x-rayed when within the pods, though this conflicts with the comic source.