How do i represent a creature made of minds?

I'm a first time dm and one of my bosses is a satyr skull animated by the minds of the people he consumed. now, i don't exactly know how his body manifests, and therefore how i should describe it to the party. i don't really want him to be just a floating skull but i don't know how to give the idea that he is made out of minds. please i would really anyone's help