The Luminoth are an ancient technologically advanced bipedal moth-like species which has an intense spiritual fixation with light.
According to their legends, they were "born between the stars," searching for a home planet for a very long time. During their travels, they met the Chozo, and exchanged technologies. They then found the planet Aether which they colonized and made their own in a short time.
At some point in the third millenium, a Phaaze Leviathan crashed onto their planet, carrying extremely high amounts of Phazon. The explosive impactliterally tore the planet in two, creating a second Aether, known as Dark Aether, on which all the Phazon concentrated. On that planet, the beings known as the Ing thrived. They found portals to Aether and invaded it. After a nearly a century of war, they were defeated and peace came back to Aether.
Source: Metroid Universe