The Hollow King #2 by Jessica Thorne
Like deep dark water, it pulls them down. The faint fire of magic within them flickers and dies. Their eyes turn black as night. They are nightborn now.
“The room is small and dark. Row upon row of jars line the shelves, each one sealed with blood-red wax. The seal’s mark is a twisted circle of briar with gleaming, gold-tipped thorns. And in each jar a flicker of forbidden magic dances… beautiful, but deadly.”