What is a monster house in mystery dungeon?

In Pokémon Mystery Dungeon games, a monster house is a special type of room that contains a large number of enemies. Monster houses are usually encountered randomly, but there are certain conditions that can increase the chance of finding one. For example, monster houses are more likely to appear on higher-level floors of dungeons, and they are also more likely to appear if the player takes too long to clear a floor.

Monster houses can be dangerous, but they can also be rewarding. If the player can defeat all of the enemies in a monster house, they will be rewarded with a large amount of experience points and items.