The Mimics sprung up in the Second Age of Hollowstar as rivals to the Metromages. Instead of the widely diverse powers of the Metromages, they all have a single flexible ability: A Mimic can replicate any action he has ever seen, but after performing it, can never do it again. Despite the equivalency of all Mimics, certain Mimics rose up as leaders.
Radam is unique in that he had an opportunity to travel through time and see many great miracles. Thus, he is able to duplicate mighty feats such as the destruction of Sodom and Ghemorrah or the parting of the Red Sea. These miracles, along with his being one of the first Mimics, earned him the leadership of the Mimics.
Though his knowledge is widely considered superior to Radam's, Khazid never became a leader of the mimics - due in part to his hermit tendency. Khazid found several creatures with the ability to magically grant abilities, and with careful planning surpassed the great limitation of mimics, that is, to only use an ability once.