In the Disney version of Rapunzel (Tangled) the step-mother uses some sort of magic song to gain youth from Rapunzel's hair, so I am wondering if Sybil needing Cress's blood is going to be something similar. Although, I have no idea why she would want the blood of a shell. Maybe it helps with her beauty or something. What do y'all think?
Also, if you have not already read the first chapter of Cress, you can find it here .