The story follows bounty hunter Samus Aran after she is sent to rescue Galactic Federation Marines from a ship near Aether, a planet inhabited by a race known as the Luminoth.

Nintendo launched a viral marketing campaign that included several websites written as if taking place in the Metroid universe.

Metroid Prime 2: Echoes is an adventure game "with heavy action elements and an emphasis on complex puzzle-solving" in which the player controls the Samus Aran from a first-person perspective.

Equipment players collect include the Screw Attack, which allows Samus to somersault in midair and off certain surfaces, and new beam weapons that have limited ammunition.

One, also seen in the previous game, is a scanner that searches for enemy weaknesses, interfaces with mechanisms such as force fields and elevators and retrieves text entries from certain sources.

[15] Multiplayer in Echoes features the same control scheme as the single-player mode, including the lock-on system for circle strafing while targeting.

Five decades before the game's events, a Phazon meteor collides into the planet and leaves a scar, causing environmental damage and splitting the planetary energy.

[19] Dark Aether becomes home to the Ing, cruel shapeshifting creatures who intend to destroy the Luminoth, and are able to possess bodies of the living, the dead, and the artificially intelligent beings.

The Pirates had previously tried to weaponize the substance after it contaminated the planet of Tallon IV, but their efforts were thwarted by the bounty hunter Samus Aran.

[20] Upon returning to Aether, Samus learns that the Marines were attacked and killed by Ing-possessed Splinters, and decides to enter a nearby alien temple structure to look for clues.

[20] When she reaches the structure, she meets U-Mos, the last remaining sentinel of the Luminoth,[21] an alien race that have fought against the Ing for decades and are now on the verge of defeat.

Samus goes to three regions—the Agon Wastes, a parched, rocky, desert wasteland region; Torvus Bog, a drenched swamp area that houses a partially submerged hydrosubstation; and the Sanctuary Fortress, a highly advanced cliffside fortress built by the Luminoth filled with corrupted robots that serves as the Ing hive in Dark Aether—to retrieve the Light of Aether and return it to the Luminoth temples.

[27] They also implemented the Screw Attack and wall jumping features seen in previous Metroid games, which were not incorporated in the first Prime due to time constraints.

[30] The developers sought advice from the producers of the Nintendo game The Legend of Zelda: A Link to the Past, which also used the theme of parallel worlds.

[31] Two bosses were made more difficult in the final days of development following a request by producer Kensuke Tanabe to "make it tighter".

Wikan regretted this decision, and when adapting the game for compilation Metroid Prime: Trilogy took the opportunity to make those battles easier.

[38][39] Nintendo launched several websites to initiate a viral marketing campaign for Echoes,[40] with inspiration drawn from Halo 2's alternate reality game I Love Bees.

[41] The websites included Luminoth Temple, an Internet forum; Channel 51, a conspiracy theory website that featured grainy QuickTime videos of Metroid Prime 2 as if it were footage of extraterrestrials;[40] Orbis Labs, which sold a "self-contained armored machine" called "Battle Sphere", similar to the Morph Ball;[40] and Athena Astronautics, which advertised sending women into space, featured a blog,[42] and offered job positions for bounty hunters on Monster.com.

Athena Astronautics gave a random selection of 25 people who replied to the offer an "interactive training manual", which was in fact a free copy of Metroid Prime 2: Echoes.

[44] The credit system from Corruption is also included to unlock the original bonus content, as well as the ability to take snapshots of gameplay.

[3] IGN's Matt Casamassina called the gameplay "superb" and "nearly flawless",[6] and Vicious Sid of GamePro praised Echoes as "an extraordinary return to form".

[4] GameSpot and IGN praised the campaign as a lengthy and rewarding adventure and appreciated the minimum 20 hours required to complete the game.

[56] The theme's dynamics between dark and light was lauded by GamePro, along with the "simple, quirky, and ridiculously addictive" multiplayer mode.

[6] The Guardian's Nick Gillett found the game entertaining and stated that its maps, terrain, and bestiary made for an amazing epic space adventure.

[52] IGN was critical of Echoes' graphics and noted that the textures sometimes blurred when viewed up close, and the frame rate occasionally decreased.

Publications including IGN and The Independent considered the gameplay too similar to Metroid Prime,[6][59][60] while GamePro was unhappy that the game did not have a customizable control scheme.