Long before Halordes was worshipped as a god he was captured by an illithid community to be made into a host for the Elder brain. They did depraved mental experimentation to ensure that he would prove an ideal host leaving him with minor psionic capabilities. With all of his strength and malice Halordes broke the bindings constraining him, sealed the Elder brain within the beings own pool of brine, and slaughtered every single mind flayer inside the hive. Left scared in body and mind, Halordes knew what to use the Elder brain for.
Now the dead brain hangs up within his private chambers as a device for channeling his own psionics through to communicate to his followers at all times. Using his psionics he communicates ideals and promises into naïve souls to be indoctrinated and help his goals.