This is the story of two werewolf/demigods, daughters of Apollo and the werewolf Leda. One of the twins, Amari, grew up in the care of a foster family, chosen by Chiron, the Centaur from Camp Half-Blood. Delta, the other twin, grew up with her mother, as a werewolf. When Leda dies, Delta finds her way to Camp Half-Blood, with the idea of vengence on her mind. She plans to kill her own twin, who has no idea she even exists.
22 parts