Engine of Purgatory
The New Covenant is no stranger to cruelty, however it is something they save for those they find deserving, though dark chapters in their past have led to unneeded cruelty and rightfully unjustified and completely wring actions. No Empire is completely clean though. This device however is saved for only those who deserve it, and is considered one of the most feared type of punishments in the New Covenant.
The Machine itself is rather ornate and takes up about as much space as a tall bedside table. It however is very heavy and solid, having advanced technologies within that are completely not understood except for the few who build them. They are commonly decorated in biblical fashion depicting a circle of hell as described by Dante the writer of the Divine Comedy. Depending on the specific sin that the criminal, or more likely monster at this point, has committed determines which Circle of Hell decorates the device. The top of the device has a dome that is also decorated, and a small viewing port into which a chamber can be viewed. This chamber is large enough for a Human head to be placed within, and depending on the Circle of hell, the inside differs as well.
The Device itself is an extremely powerful simulation device that require the living head and brain of the criminal to be interred in the dome on it, where once plugged in they are given virtual immortality. The technology interfaces with the head and keeps it perpetually alive, as the still living person begins to interface with the simulation in which they shall receive their eternal punishment. As said before the inside of the dome will differ with the punishment they receive, and it is meant to be directly symbolic of that.