Drawing comparisons to titles such as Wizardry and The Bard's Tale,[1] Etrian Odyssey challenges players with exploring and mapping a vast dungeon. In classic fashion, players navigate through the dungeon a single "step" at a time, moving and turning in fixed increments. Time passes only when an action is taken, causing movement, random encounters, and combat to all be entirely turn-based. The game uses a first-person view to present the dungeon using a combination of relatively simple 3D computer graphics for environments and single-frame 2D sprites for enemies.

As in the era prior to the inclusion of automatic mapping in the genre, Etrian Odyssey requires that players maintain their own map. However, rather than doing so on a separate sheet of graph paper, players do this by directly annotating (with the stylus) a small map displayed on the DS' touchscreen. The accuracy of the map is entirely controlled by the player, so he or she is free to map accurately or haphazardly. However, since the ability to successfully navigate back out of the dungeon (in order to save the game by returning to town) relies on keeping an accurate map, doing so is highly advantageous.

While many console role-playing games ask the player to control pre-existing characters with their own unique characteristics and personalities, Etrian Odyssey requires players to create their own characters from a number of different character types (classes). Each character type has at least one special skill or aptitude. While only five characters can be in the party at a single time, a much larger number can be created and kept in waiting back at the "guild hall". Characters can be switched in and out when in town, so if a given specialty is needed for a specific obstacle, the party can be tailored appropriately. The player customizes characters by allocating skill points to specific skills during level advancement.

The title was first announced by Atlus through Famitsū after demonstrating it behind closed doors at E3 2006.

The development team within Atlus was led by Kazuya Niinou who also directed the development of Atlus' first in-house game for the DS, Trauma Center: Under the Knife. The game features character designs by Yuuji Himukai, monster design by Shin Nagasawa, a story by Shigeo Komori, and FM-like music by Yuzo Koshiro.

The game was originally to be released internationally as Yggdrasil Labyrinth, but was renamed to avoid any possible confusion with Yggdra Union (a game published in North America by Atlus a year earlier) or Deep Labyrinth.[2]

Towards the end of 2007, Atlus announced a sequel to Etrian Odyssey.[12] It was reported that the game would feature 12 job classes and that Yuji Himukai, Makoto Nagasawa and Yuzo Koshiro would reprise their roles, with Shigeo Komori taking on the role of director. All original character classes are included, along with three new classes: Beast, Gunner, and War Magus. Screenshots were released showing that the mapping system has been improved, with new symbols that can be added to the map for more detailed and accurate maps.

The sequel was released on February 21, 2008 in Japan. It was later released in North America on June 17, 2008, under the title Etrian Odyssey II: Heroes of Lagaard.