During the Darkarian fall from Expletun society (rather their own separation of such during the time where a division of thought occurred) they began to think up their own set of races to combat the Expletuns Chosen races. While this was prior to the Hive mind being Borne, these races would be their own champions. All of these races are Metamorphs, making them difficult to detect and combat.
Of these, the Sauren were created. In their humanoid form they appear like Terrans (a compatible species and denominative sentient base amongst species) and basically function as one. Their psionic ability in this form is none. One difference, is that Sauren have difficulty controlling their temper and are enraged easily. This causes them to metamorph into 8ft lizard like versions of themselves. As a Metamorph, they are adept in Clairsentient psionics and are extremely vicious.
