"The Blood Mirror" is the fourth book in the Lightbringer series by Brent Weeks. It continues the story of Karris White and Gavin Guile as they navigate political intrigue and personal challenges in a world where magic is based on the manipulation of light and color. In this installment, the characters face new threats and revelations that test their loyalties and beliefs. The narrative explores themes of power, sacrifice, and the consequences of choices, while introducing new characters and deepening the complexities of the existing ones.