Rescue four allied soldiers from the four cells in Castle Prevant. All of the cells are located on the first floor of the castle. Cell 1 is the first cell on the left; cell 2 is the second cell on the left; cell 3 is down the hall from cell 2; cell 4 is at the end of the hallway past cell 3.
Cell key 1 is dropped from one of the first Order Jailors you kill in the castle. Cell key 2 is in a chest in a room to the south of your starting position. To get there from the starting hallway turn right, follow the hallway until you reach a 4 way junction, take the left, and then turn left into a room with the chest. Cell key 3 is given to you by a mouse that is hidden under a stone gargoyle on the second floor. You will need Rico to get this key and a sunstone. Cell key 4 is made by Edward using marble and Iron Metal. Marble can be found in a hidden chest on the second floor.
After all this you will gain a Situation Bonus and 3500 experience.