Genericons are prisoners sent into the Slayers environment, with a set of pre-programmed actions, with no one controlling them. They have no way to react and it is suggested that their chances of survival are next to nil.
Castle defends this practice by arguing that there are plenty of men and women in prison who could never cut it as Slayers but should still be given a chance to roll the dice for a ticket out.
To gain their freedom Genericons only have to survive one session.