A thrall is a mindslave of the Illithid. The Illithid keeps them as food and menial workforce. The different Gith races were ones thralls, but shook of their chains and became free.
The dark is that the Multiverse rages against uniformity, and parcels infinite fiefdoms to the greatest dichotomies- be they of Substance, or of Essence. It is both expected and comical that these dichotomies seek mutual extinction.
