The Purgatory-class prison ship was the modified version of the Porter-class transport.
Over a kilometer in length, the design was blocky, box-like, and slow, but functional. However, the ship performed poorly if pressed into combat.
The Purgatory wasn't able to go into the atmosphere, but equipped with two landing bays, each housing three Peth-class transport shuttles and two TIE-fighters.
The prison blocks were composed of many ten-prisoner cells, equipped with uncomfortable bunks.
Being unsatisfied with the conditions inside the Porter-class troop transports designed for the Clone Wars, Rothana Heavy Engineering modified the ships into prison vessels for the Galactic Republic and renamed them the Purgatory-class.