By the time Mattheus changed out of the guise of Arsenio Leblanc and arrived at the palace, he was pulled into the aftermath as Court Healer.
What was known as the royal palace was actually a collection of buildings referred to as the collective term. There, in fact, were multiple "palaces" across the grounds.
The main palace was where the Chamberlain's Office and Mattheus's office was located. It was where the throne room and largest ballroom were placed. A busy area with a lot of foot traffic that used to be the original castle of which the first of the Morgaine family and retainers resided.
The Duchess—the King's younger sister—and Queen Genevieve resided in the western and eastern palaces respectfully.