Onyx Inferno is the younger sister of PC Amethyst Inferno. Onyx spends a lot of her time with Blaze, so she is simultaneously childish even though she is beginning to come into her own as an adolescent. Onyx looks up to Amethyst a lot, even though she doesn't necessarily let it on.

Onyx Inferno is the youngest sister of PC Amethyst Inferno.