Ok thank you both for the help. You helped me approach the questioning in a different way and I found the book. blood was the key as well as the priestess sacrificing her.
The Cerulean by Amy Ewing.
An exploration of feminine power, autonomy, and sexuality.
Nearly 18, Sera has led a protected life in the City Above the Sky, an all-female society connected to a planet via a magic tether. Her race of Ceruleans possess blue hair, blood, and eyes and silvery skin. Sera is chosen to sacrifice herself by jumping off the edge of the City to break the tether so that her people can locate another planet with resources to draw upon. On the planet below, 18-year-old biracial human twins navigate another culture’s social restrictions. Leo, who appreciates women and fashion, takes after their Pelagan mother with his blue eyes and light skin, while Agnes, who is attracted to women (in a homophobic culture) and loves science, resembles their Kaolin father with her brown skin and eyes. The two go on an expedition to collect another specimen for their ruthless father’s popular theatrical freak shows and come across Sera, who never could muster the romantic feelings for girls her society expected, following her crash. Most citizens of Kaolin are brown-skinned, while the Pelagans are predominantly fair-skinned. In places, the text appears to unquestioningly privilege lighter complexions. In alternating narration, Ewing (The Black Key, 2016, etc.) provides intricate, well-explained worldbuilding, slowly unveiling a deeply buried mystery and leaving characters poised for new discoveries.