The Four Kingdoms series by Whitney Dean

 At ten years old, Raven was mysteriously willed to be the next ruler of Seolia, a kingdom nestled within the realm of The Four Kingdoms. Orphaned as a baby, she has spent fifteen years ruling over a kingdom she believes she did not earn all while hiding secrets: she possesses dark magic, and she thirsts for blood.

Now at almost twenty-five years old and with a sudden addiction to stealing life, Raven must fight through her new procured darkness to save her soul, but when a mysterious stranger arrives in her kingdom, she starts experiencing vivid dreams that detail who she truly is. As she slowly starts to unravel her story, what she uncovers at the end of the spool will change the course of her life and her kingdom forever.