A border military prison surprisingly has a regiment stationed nearby, and the prison itself has an unknown number of guards. More terrifying is that there are actually three dark fortresses and a tunnel at the entrance. The tunnel connects to the trench, which is easy to identify, but where it leads is unknown. If it connects to the nearby military camp, it means a regiment's force can continuously support through underground without worrying about outside weapon obstruction.
The prison has only one entrance, which is the main gate, surrounded by high walls with barbed wire. During the day, dead birds are found hanging on the wire, already burnt, indicating there's electricity. Although there are blueprints of the two main buildings inside, and the general troop deployment is known, the confidence in a strong attack is extremely low. If the nearby military camp reacts, no one can escape.
