Queen Katherine de Monpezat (née Illéa) is a historical character mentioned in The Elite.
Katherine was the only daughter and eldest child of Gregory and Bethany Illéa, and the sister of Spencer and Damon. Katherine lived a wealthy life with her family, but was eventually forced into an arranged marriage with Emil de Monpezat, who was the crowned prince of Swendway, a man much older than her, for her father's greed of power. After her marriage to Emil, she became a princess and her family became royalty, making her father king of Illéa.
In his diary, Gregory noted that Katherine cried a lot before the wedding, but he showed no sympathy and told her to straighten herself out or she would pay the consequences. He also noted that his family was not happy about the marriage after they realized it was forced. Her younger brother Spencer soon realized his father's plan to become the king himself. He knew that the same was expected of him, but he couldn't do it. So, he faked his own death and ran away. He hid with relatives and friends, eventually making a camp with some like-minded people in the north and becoming the founder of the Northern rebels. His younger brother Damon became king instead.
It was implied that Katherine was shipped to Swendway with her new husband, was eventually crowned queen, and had a daughter named Antonella.