The cell is a 2x2x2 box with water on the floor. There is a perfectly-placed end crystal to prevent mining out. In the floor there are hopper minecarts to pick any items up, and the prisoner respawns from below using the squilly bed glitch and a shulker. If some method is used to cause respawn to be above the shulker, suicide will activate.
Outside Defence
Above the prison is a mining detector, and below there is a pearl glitch detector at Y=1. There are 8 permanently active area bans around the central chunk.
Other Security
When any portal is active a temporary area ban activates that is in range of the portal, so the guards in a safe area can see if anyone unwanted comes in.
