Just as Hao Ren had guessed it, the castle on the hill was Vivian's place of hibernation.
Specifically speaking, it was the entrance to her hibernation chamber.
After a rigorous discussion, Hao Ren and Hessiana had revised their plan to remove the seal and enter the shadowy realm. Without wasting time and before the demon hunters caught up with them, they decided to enter the castle before dawn. The shadowy energy at night was intense, and it made seal-removal difficult, but Hessiana still chose to use her Shadowmancy in place of the key. She was not worried because her power only became stronger at night.
