Etrian Mystery Dungeon is a collaboration title crossing the world of Atlus's Etrian Odyssey series with the roguelike gameplay of Chunsoft's Mystery Dungeon series. It features familiar character classes and skill tree mechanics from Etrian Odyssey alongside a labyrinthine approach to the randomly generated Mystery Dungeons.
As is traditional of Mystery Dungeon, the game takes place mainly in dungeons made up of randomly generated tile-based floors. For every action the player takes, including movement, attacking, and usage of items, all enemies on the floor will also take an action. Players can progress through the dungeons by finding the stairs located on each floor. Unlike most other Mystery Dungeon games, which use a linear dungeon floor structure, this game's dungeons feature multiple sets of stairs per floor that lead to divergent paths. Etrian Odyssey's F.O.E.s also make an appearance as D.O.E.s, large enemies that will move from floor to floor of the dungeon as they progress towards the surface. To protect the town of Aslarga that acts as the player's main camp, it is necessary to build forts and keep watch for these monsters.
Going further through the various dungeons will grant access to stronger enemies, materials, and equipment and bring your guild closer to uncovering the mystery of Yggdrasil's dungeons.