Manster was under the rule of the Freege family, a house of nobles put in charge of Northern Thracia by the emperor of Grannvale Raydrik, who was once a general of the Kingdom of Conote, was assigned watch of Manster by Lord Bloom of the Freege family.
Leif had no idea of what he was about to witness...
The Dungeon is Chapter 4 of Fire Emblem: Thracia 776.
Despite its small size, there is a huge amount of factors to take into account. Leif, Karin, and Felgus are in the lower left hand room, Lifis and three brigands are in the lower right room, and in the left and right corner rooms are civilians (movement range 4).
Unlocking the civilian's cells will have them head for the nearest exit (upper left hand cell's prisoners head for the west exit, upper right hand prisoners for the east exit). Take caution to free and equip Leif, Felgus, Karin, and Lifis, however, for enemy reinforcements will come from their exit points. If all prisoners are freed, you will proceed to The Hero of Winds, where you can find extremely valuable assets, such as Asvel, a Brave Sword, and the Sety Scroll. However, the soldiers in the area will capture them whenever they get the chance, and if they're taken to their exit points by their captor soldier, they will not be saved and you will not proceed to chapter 4x.
The Soldiers in this area present a threat not in quality but in quantity. Proceed fast, as their reinforcements will compound with enough turns.
The Brigands in Lifis' cell will attack the Soldiers, keeping the duty of fending off soldiers aided, but it is only a matter of time until they are either killed, captured by an enemy soldier, or escape.
Be absolutely prepared before you unlock the north door. An ambush is lying in wait behind it, including Dalsin. If Yubel was rescued in chapter 3, talk to him with Leif to recruit him.