Dark Luminoth

A Dark Luminoth is a Luminoth that has been possesed by the Ing Horde. Many Luminoth, after finding out that the Ing Horde posses their own, the Luminoth had stated that they would rather "Self Terminate" than become a weapon for the Ing. Although they are mentioned in Luminoth Lore, they are not actually seen during gameplay. Below is a screenshot of what appears to be a Dark Luminoth, seen in a beta trailer for Metroid Prime 2: Echoes; not seen in the full version. It is likely just an early model for the Luminoth, however.