In Metroid Prime 2: Echoes, the hostile race from Dark Aether that fights the Luminoth is the Ing.
The Ing are dangerous, shapeshifting beings native to Dark Aether, the alternate dimension created when a Phazon meteor struck the planet Aether. The impact split Aether’s planetary energy between the two realities, leaving Light Aether and Dark Aether locked in a struggle for survival. The Ing seek control of that energy, while the Luminoth attempt to reclaim it and preserve their world.
The Ing are especially threatening because they can possess living creatures, corpses, and artificial intelligences. Their attacks have nearly destroyed the Luminoth civilization by the time Samus arrives. She works with the Luminoth sentinel U-Mos to recover the stolen energy from dark temples across Aether’s regions.
The conflict culminates with the Emperor Ing, the most powerful member of the species, guarding the final portion of Aether’s energy. Chozo are an ancient species tied closely to Samus’s history, Diamonts are a separate race represented by the bounty hunter Spire, and the Kriken are represented by Trace in Metroid Prime Hunters.