Further to my Grand Unified Severain Theory that's captured the hearts and minds of this list (please, no autographs) it has struck me that if the Hieros are part abo, or if their morphing ability is the result of Number Five's splicing of human and abo DNA, then the extermination of Urth's indiginous population and its replacement with abo-spliced human stock would in fact count as their revenge upon the humanity that created them, given the extermination of the abos by human colonists so long ago.
Ori