The Prison of Elders is Destiny's most honest acknowledgment that the Guardians are operating inside a moral framework they did not build and have not examined. The prison holds the enemies of the City, which means it holds whoever the City decided to imprison, which means the warden is not justice but custody. The Servitor awaits because it has always awaited, because the prison runs on systems that do not require a Guardian to maintain them. The session is about going in and coming out, which is the only thing the Prison of Elders has ever asked.