The models used by the Galactic Empire were equipped with universal energy cages, holding cells, drop bays, and sparring chambers where Dark Side Adepts could battle captive Jedi. They were designed to intimidate, and gained a reputation for never returning a captive who entered them. Guard droids were used to help prevent Jedi escapes.
In order to ensure that prisoners couldn't revolt and commandeer a vessel, their navicomps only were able to hold two sets of coordinates, the home base and the destination, and so could only go to those locations. Though the Lictor class wasn't manufactured for combat, it did possess 10 quad turbolaser batteries and two tractor beam projectors for self defense. In addition to the MandalMotors design, there was also the scaled down Kiltirin-class, manufactured by Rendili StarDrive.
The Lictor-class was used to transport normal and Force-sensitive prisoners, such as captured Jedi Knights during the height of the Great Jedi Purge following the Clone Wars. The Revelator was dispatched to accompany Inquisitor Valin Draco on a mission to the Cularin system, not long after the end of the Clone Wars.
During the aftermath of the Imperial Civil War in 10 ABY, Jedi Master Luke Skywalker and R2-D2 were transported on an Imperial dungeon ship to Byss, the secret throne world of the "reborn" Emperor Palpatine. By that time, a dungeon ship could be purchased for 7.8 million credits.