MTT

MTT are a highly invasive species, living to assimilate other species. They are notoriously hardy and able to survive in hostile enviroments.

They have arrived on earth some years ago, along with the Yol they have assimilated already, hoping to call earth home, and assimilate the humans while they're at it.

This does not mean that all MTT live only to assimilate their companion races. Most MTT are simply trying to survive in their own ways.