The King Demon summons a bride as a way to increase his power and control over the Demon realm. The bride's pure spirit and innocence can help to balance the dark magic of the Demon King, and their union can increase his strength and influence over other demons. In addition, the bride can serve as a conduit for the King's power, enabling him to access her energy and channel it towards his own goals. The King Demon needs to carry his future children with his bride.