Her violent murder resulted in Poly's returning to the material plane as a vengeful "wraith". Having managed to stray from the path of revenge, the pacifist ectomorph spends her nights trying to help the living stay that way.

Dan notes:
Polychrome was partly inspired by the L.Frank Baum character from the Oz books – Polychrome, the Rainbow's daughter – but mostly she began as a creature that was both angel and ghost - meant to be a contrast to some of the more violent or aggressive characters in the stories. She's kind of evolved as this cool big sister.