King is just a title
There were many things that needed to be done before Bryce could think about other things, but in his mind the top priority was obtaining the blood powers that he believed should have rightfully been his in the first place.
He wouldn't let anything get in his way and most of his resources were placed into this task.
Using the influence skill on Cindy was relatively easy and the main reason for this was due to Quinn's shadow eater skill. With that, she was no longer the vampire she used to be. It made her whole body weak and this also made extracting information from her quite easy.
With this, they had gotten information of where the book that would store the absolute blood powers was kept. Unexpectedly it was hidden in an expected place, in the second castle. It seems like Cindy was arrogant that either one, her plans would have never been revealed or the second, that she would succeed so there was no point attempting to hide the book.