“A Galactic Federation ship has disappeared in pursuit of a band of Space Pirates.  At the request of the Federation, Samus journeys to the planet Aether, the location of the ship’s last transmission.  There, Samus finds herself in an incredible world where Dark and Light intertwine in two unstable dimensions.  The Light World is controlled by the Luminoth, a peaceful tribe with a unique and highly developed civilization.  Their four gigantic energy generators are all that keep the Light World from collapsing.  But that civilization faces imminent destruction at the hands of the Ing Horde, beings born of the Dark World.  If the Ing seize control of the generators, the Light World will be extinguished forever.  Samus embarks on her mission to defeat the Ing and restore peace on Aether.  However, there is an ominous shadow lurking in the darkness, a shadow which is quietly stalking Samus.”

Straight off of the press which is known as Nintendo Power is the story of Metroid Prime 2: Echoes.  Edited slightly, here is what the Nintendo Power writers had to say in Volume 181:

"After landing on the new planet of Aether, she'll find that it's taken an apocalyptic hit from a Phason meteor that's caused a dimensional rift.  So she'll explore the dual worlds of Light Aether, where the peaceful Luminoth fight for their lives, and Dark Aether, from which the ciolent Ing spawn.  Though the Phazon-hungry Space Pirates are in full force on both realms, the new Ing may trump them for sheer vileness, able to decompose into inky shadows that spray through the air to recompose elsewhere.  Creepy.  The two worlds also tie into Samus's new Light Beam and Dark Beam with an innovative dual-ammo system that will keep you on your toes.  In perhaps the hugest surprise, Metroid Prime will include a Metroid first: a multiplayer fragfest in which bounty hunters gun for each other, grapple across ceilings and go ballistic as Morph Balls.  No doubt, Metroid Prime 2 will dominte 2004."