The toy was undoubtedly enchanted; while it wasn't anything she was familiar with, directly, it seemed to have some elements of transmutation magic, associated with gender. It seems that, with a command word, it could be attached to a female, and would modify itself to function virtually identically to male genitals, as long as it remained attached. A separate command word could alter whether or not the emissions from it could cause pregnancy; it was currently in an 'off' state. Apparently, Minurra didn't want to get Rimeera pregnant, herself, instead hoping the succubus would succeed.