Perdition

Aaron Gromar, former UFC Senator who’d lost favor with the new world
order, is warden to Androneda Prison, a remote planet which takes five
years to reach in a ship with FTL drive, but he is as much a prisoner as
the inmates. He can never leave. Aaron is a strong man with a dark
secret he dare not reveal as it would mean his death.
Apart from the occasional use of an isolation cell, there is no need
for bars in Androneda’s Prison. Staying alive from day to day is enough
deterrent to misbehavior for most prisoners. That, and a device called
Lobe-O. The only sure escape from this planet is death.

It’s been tried.

Berina Colchek is sentenced to life on Androneda, better known as
Perdition (Eternal Hell). She’s an assassin, inured to killing. The one
emotion, perhaps the strongest she feels, is anger. Her anger and hatred
is directed at the Warden Gromar and all he stands for, but she soon
discovers quite a different enemy facing her she never counted on.
Perdition is everyone’s enemy, and the struggle to survive its daily
torments is a vital priority for staff and prisoners alike.
One thing is certain. If you’re human, Perdition will either make you
stronger or destroy you utterly.