Zarum was a Illithid Empire once located on Charos, which was destroyed over 10,000 years ago.
Eons ago, the dreaded Mind-Flayers controlled much of thw world of Charos. For thousands of years, their vast Empire spanned whole continents and hundreds of cities. This empire may have been controlled by the Ilithids, but was built by the Gith; a pitiful slave-race that were exploited by the Mind-flayers as both labor and food.
The far-flung empire of Zarum seemed invincible, but along came a young slave called Karzi, who slew her Ilithid master after she learned the secrets of fighting its terrible mind-control powers. She and her followers then began a rebellion that soon spread across the IIithid Empire. The uprising lasted centuries, and millions of Gith perished.
To quell the rebellion, the Illithids used enormous armies of mind-controlled Gith against their own people. The freed Gith were then forced to fight legions of their brothers and sisters who were still enslaved by their Illithid masters.
The war was bitter and the vengeful Gith slaughtered every single Illithid they could find. Whole cities were destroyed and great regions of Charos were laid waste.
Finally the Illithids were defeated and their extermination seemed close at hand, but a Gith general named Zerthimon betrayed the Gith people by murdering Karzi, causing the two sects to be estranged and eventually become two separate races called the Githyanki and Githzerai.
From that point onward, those two races were ever at war with each other and they hated each other as much as both groups hated the Mind-Flayers. It was only because of this dissension that the Illithid race survived, although they were far weaker and fewer than they had been.
Most Illithids were forced to flee Charos and found refuge in the Underground lairs they now inhabit. Today, however, Githyanki hunting parties are increasingly vigilant, thus, Illithids are never really safe anywhere.
