Queen Aggravain is a character from the musical "Once Upon a Mattress," which is a comedic adaptation of the fairy tale "The Princess and the Pea." She is portrayed as the overbearing and controlling mother of Prince Dauntless, who is determined to find a suitable bride for her son. Her character often creates obstacles for the princesses who seek to win Dauntless's heart. In the story, Queen Aggravain sets impossible tests for the princesses, showcasing her desire to maintain power and control over her son's life. Her antics add humor and conflict to the narrative, ultimately leading to the arrival of Princess Winnifred, who challenges Aggravain's authority and expectations.