The sequel to Obsidian, Onyx begins in trigonometry class, with Daemon telling Katy that they have plans. Again. Ever since Daemon healed Katy, they have been connected. Their hearts beat out the same rhythms. They can sense one another. And Katy can destroy and move things without trying. Just like Daemon. This connection seems to be annoying but Daemon seems to enjoy the time he can spend with Katy. He tells Katy that she will admit that she is "madly, deeply, irrevocably and irresistibly" in love with him by New Year's Day. Katy knows that deep down, she does have feelings for Daemon. Nevertheless, she puts on a smirk and is determined to make sure that she wins. Meanwhile, in biology class, she meets Blake, a normal, human boy, right? Wrong. Blake is just like Katy--healed by a Luxen. Blake offers to help Katy harness her powers and though Daemon seems skeptical, Katy agrees. During the time, the DOD (Department of Defense) comes to the area. This poses as a bigger issue than the Arum, especially as Katy and Daemon find out that the DOD may not be after Luxen or Arum. Written in Katy's perspective, readers will have trouble putting this novel down.