Githzerai
History
Once upon a time (in da future) the mindflayers were being titanic douchebags. Is anyone surprised? You? Well, go screw yourself, that's just how they roll.
Anyway, this particular time, they were using mindcontrolled humanoid slaves to work the wheels of their titanic, world spanning empire. These slaves were either the first race ever to come into being, or heavily mutated humans, depending on which version of the fluff you read.