Illithids

Illithids are bred in a spawning pool as slug-like creatures that inhabit the bodies of other races like parasites until they fully mature and mutate the host into a fully grown illithid. There are 5 castes of Illithids. Alhouri, the Hive Lord, is the most powerful of all the illithids in the hive. They are the center of the hive-mind collective. Should the Alhouri be killed, the hive will turn berserk. Illithari are the most common type of Illithid. They are the drones who venture out to hunt and gather food, resources, etc. Heavily Psionic, but lacking in most other qualities. Ulitharin tend to be the most powerful of an illithid hive. Generally, when an Alhouri dies, an ulitharin will sometimes replace the previous and take control of the hive, becoming the next Hive Lord. On top of their psionic powers, they are well versed in magic as well, more commonly becoming Thaumaturgists, though some are masters of Sorcery. Illithane are the rogue caste; specializing in assassinations utilizing a psionically manifested weapon, the Soul Knife. The creation process of a Soul Knife is a talent most psionic races are incapable of, or have an incredibly difficult time creating. An illithid's biology gives them a distinct advantage over the others. Finally, the Thoorian are the warrior caste. These are the front line soldiers, defense and hunters of most hives. Due to the nature of psionic creatures, they have a distinct advantage over others, not because they are tougher than most, but specifically from their ability to manifest psionic armor.
The Caste Hierarchy: Alhouri - Hive Lord
Ulitharin - Mystics and Prophets
Thoorian - Guardians and Warriors
Illithane - Hunters and Interrogators
Illithari - Drones and Gatherers
Illithids do not view the concepts of good and evil like most races. They will always do what is necessary for the betterment of the hive. They are willing to work with other races, so long as their goal is not undermined. In the cases where others attempt to double cross them, most hives will seek retribution in the form of enslavement.