Dozens of feet tall, Madame Majestrix, the queen and ruler of Monstro City, strikes every bit as imposing a figure as the power at her disposal warrants. She and her subjects have threatened humanity numerous times over the decades. She is also the mother of Rex of the First Family.
Her battle with the First Family over ownership of the Gemension Jewel led to the siege of Monstro City by the Trenchers. Ironically, the jewel itself was mysteriously and surprisingly transported elsewhere, to some unknown location.