dave2008
Legend
Third idea, related to #2. Create a central overpowering threat - something that can't be beat (at least not now). May their jailer is a Huge demon/devil that pursues them through hell. Perhaps the "game" starts with this giant fiend reaching into the cell and picking out a random person (could even be one of the PCs) and consuming them in front of the whole group. It is, or almost is, a cut scene. The adventure starts, you describe the surroundings and, boom, a clawed hand reaches down, grabs a inmate, raising up the monstrous head of the beast and is bitten in half. The beast gulps down the blood flowing from the torso, throws the remains back in the cage, and then moves on to the next cage. Then have this fiend chase them through hell when they escape their cage. Can the get out of hell before the beast picks them all off?