Illithids are a parasitic slaver race that needs other races to exploit. They use them as labour, reproductive hosts and meals.
Githyanki are a militaristic race of "space pirates" who raid worlds steal what they want, kill those who try to stop them and go away to enjoy their plundered goods. They sometimes take slaves but once their usefulness is at an end they either kill the slaves or just forget about them.
Both are bad. The Githzerai are the way! :P
