Monster House

Monster Houses, called "MH" for short by some players, are special floors that appear at random in most dungeons (barring many in Exbel as they are typically beginner dungeons). Monster Houses are characterized by being one small room with many Pokémon in it, around 15-20, and will still spawn in slowly. All the Pokémon that appear will be Pokémon that would usually be encountered on the floor. Pokémon defeated in a Monster House will yield double the normal amount of experience. When encountering a Monster House, a text box saying "It's a Monster House!" appears before any action can be made. Monster Houses can only appear in randomly generated dungeons, and on Floor 6 and up. Items that would normally be in walls spawn on the floor in Monster Houses.

Zorua
Monster Houses are the only place Zorua will spawn, and it will not spawn on its own; a Pokémon with the move Sweet Scent is required. Zorua will only have a chance of spawning with the use of Sweet Scent, so bringing PP restoring items is a good idea. Due to Illusion, Zorua will appear as a random Pokémon on the floor if there are any, otherwise it will appear as a Zorua. Once Zorua is recruited, it will know the moves Sludge Bomb, Punishment, Sucker Punch and Nasty Plot, based on the four Event moves Zoroark can obtain. Zorua can not spawn with the use of Honey.

Trivia

 * Zorua was previously Event only.
 * Zorua is the only Pokémon that can be encountered solely through Monster Houses, discounting seasonal events.
 * Pebble Cave used to be able to have Monster Houses upon release, which has since been removed.
 * "MH" is also a slang term to refer to a room or location on a dungeon floor where there is an unusual concentration of Pokémon, usually difficult to handle solo.