The Great Prison of Mentiri

Mentiri acts as a maximum-security prison for the criminals of the Nine Hells. Inside, inmates are tortured and indoctrinated to ensure they follow the rules of the Nine Hells. This secure prison is located deep within Dis and within its walls contains many different kinds of prisoners—outsiders, captives from the Blood War, and others who have broken the laws of the Nine Hells in one way or another. The only way into the prison is being captured and condemned to rot there. The characters are lucky that they've no reason to enter.