Pokémon Mystery Dungeon series are spin-offs for the main Pokémon games in which the player takes the role of a human transformed into Pokémon and transported in a world inhabited by Pokémon only. They then progress within the game to save the world.
The Pokémon Mystery Dungeon series have begun with Pokémon Mystery Dungeon: Red Rescue Team on GameBoy Advance console and Pokémon Mystery Dungeon: Blue Rescue Team on Nintendo DS.
Following those titles were: Pokémon Mystery Dungeon: Explorers of Time, Pokémon Mystery Dungeon: Explorers of Darkness, Pokémon Mystery Dungeon: Explorers of Sky (all three on Nintendo DS), Pokémon Mystery Dungeon: Keep Going! Blazing Adventure Squad, Pokémon Mystery Dungeon: Let's Go! Stormy Adventure Squad|, Pokémon Mystery Dungeon: Go For It! Light Adventure Squad (all three on Nintendo Wii) and the last game, Pokémon Mystery Dungeon: Gates to Infinity (on Nintendo 3DS).
In these games, the player assumes the role of a human transformed into Pokémon and then transported to a world inhabited by Pokémon only. Once arrived there, the player teams up with a partner Pokémon and can later team up with other Pokémon to progress through the games.
The main aim of the game is to progress through various dungeons whose layout changes each time players go through them, and populated with wild Pokémon the player will have to fight to gain experience and become stronger.
In those 'mysterious' dungeons, player will also often find items which will help them through their journey, namely money and berries, but will also have to keep an eye for hidden traps and monster houses, special rooms filled with Pokémon, items and traps.
At the end of the dungeon, players will often be faced with the boss of the dungeon, which could be a legendary Pokémon or one of the important characters in the plot.
As the player progresses through the games, dungeons will tend to have more complex layouts and with more floors or bases to go through. Should they succumb in the middle of a dungeon, they can seek the help of other players via a feature called Wonder Mail which contains a code any other player can use to rescue them.
Like in the main series games, players are able to make their Pokémon evolve (except their own character and their first partner; they can evolve only after the main storyline is beaten) and players can obtain new Pokémon by befriending them.