The fifth floor has some hidden teleporters near the 4 main doors. You can only enter in this rooms by the right side of the door.(You must go counter clock wise to reach the rooms). In the east room you can get the Glass Key after defeating Avenger Knight. You need this key to open the south and north room. The north room is the exit of this floor. After finishing the castle, say Let's call it a day for a +1 Understanding