A ulitharid overlord is an incredibly rare version of illithid caused by a mutation that enlarged their brain. They are far superior to other mindflayers or elderbrains. They are also far more ambitious. Instead of simply recreating the illithid empire they seek to rule it. 

This Ulitharid overlord leads perhaps the largest mindflayer colony on the material plane. Ulitharid can function as elderbrains in their natural form while staying far more mobile. Their psionic power is equal to a God.