Zio was a long-serving inmate of the Akritirian prison known as the Chute, encountered by Harry Kim and Tom Paris.
Zio was one of the prisoners held in the Chute, the brutal Akritirian prison where inmates were left to fend for themselves and fitted with a neural implant called the clamp that drove them toward violence and madness. An eccentric figure, he had survived there far longer than most.
In The Chute, Zio crossed paths with Harry Kim and Tom Paris after they were falsely convicted of a terrorist bombing. While Kim struggled to keep the wounded Paris alive and to find a way out, Zio offered his own peculiar wisdom about the prison and its inmates, a glimpse of what years inside could do to a person.