Ilithids

Description and location-
The ilithids (or Mind Flayers) are a subterranean race of empire builders.
Gods-
3 Cultural Aspects-
Main personality is that of hunger.. they are always hungry, seeking meals. most ilithids are lead by an intense ferocious hunger for brains that con not be settled, leaving behind brainless corpses.
separated into 4 types. Thralls of captured slaves who have had their minds dominated by ilithid worms and kept docile by mind control of a full blood. A half blood, the evolution of a thrall as the worm consumes and integrates its host, and whos mental status is not nearly as developed and much more feral and instinctive, appears as a monstrous transition from the original race to an ilithid. A full blood, which are the true civilization of thinkers pulled from the elder brain itself. And the elder brain, a collective hive mind of all dead ilithid of the colony, and where genetic and organic material is recycled into creating more ilithid full bloods.
conquerors, not constructors. They live underground, but do not build structures or cities themselves. Instead they adopt buildings from conquered peoples, and use the former knowledge and skill of captured thralls to make any new construction, resulting in ilithid cities taking on an conglomeration of different architecture styles, telling a creepy history of conquest as old thralls are absorbed and new thralls are taken.
Reputation-
Monst do not have any knowledge of the ilithids. Refrence to the "mind Flayers" can be found in old texts detailing the elvin split a few thousand years ago, described as a terrible and powerful enemy from below, but was defeated by the elvins and then destroyed by the drow. Nothing more than old ghost stories has survived in human archives, and the elvish ones were long ago destroyed
The only nation with any real knowledge is the drow and duregard, who remember clearly their time as a race as chattel for the ilithids and the sacrifice it took to free themselves, as well as what it would mean for them to return.
Relationship with other local ethnicity's- 
The ilithids do not negotiate or work with others. All are beneath them, and will be dominated or turned to chattel.
History-
The ilithids once had an under ground empire that grew across the southern portion of the continent. They then rose up from the ground, taking mass quantities of elves, dwarves and humans as slaves and thralls. A desperate war was fought, which decimated the surface and scorched the earth. Eventually the ilithids were driven back underground, taking with them a significant portion of the surface population. The elves retreated to the north beyond the perceived reach of the ilithids. A period of 700 years eclipsed in which the captured elves and dwarves were physically experimented on and changed under dominion of the ilithids, eventually becoming the Drow and Duregard. Those two races eventually rebelled and escaped, destroying the elder brains in the process, instantly killing ilithids across the continent who were mentally linked to them. Other Notes-
Ilithids did not like sunlight or cold, the first making night attacks and ambushes frequent, and the second resulting in the elves continually fleeing north in hopes that the ilithids would not follow into the colder mountain passes.