Murky Forest is a Mystery Dungeon exclusive to the special episode, "Igglybuff The Prodigy" (to unlock this Special Episode, you must first encounter the Fogbound Lake event). Being in a Special Episode, it is only accessible in Explorers of Sky. The first time this Dungeon is explored is with Skorupi and Banette.
At the end of the Dungeon, the first time it is cleared, Armaldo the Explorer is encountered. It is said that a monster lives in Murky Forest, who is most likely Armaldo. It is 7 floors. It has traps, no rest stops, and a few Kecleon shops. There is no recruiting in this dungeon, the only time there can be more than one other Partner with you is the first time it is explored. It has the same music as Tiny Woods from Red and Blue rescue team.