The Four Towers are a set of towers scattered across the world of Monster Girl Quest. They are located at the north and south poles and on two opposite extremes to the east and west. All four towers house a generator that Promestein developed to seal and weaken the Four Spirits' influence on a global scale, neutralizing Luka's powers in the process.
Shortly after Ilias declares her intention to remake the world, Promestein confronts Luka and activates the seal on the spirits to neutralise his powers.
Later, the importance of the towers is discovered by the human-monster alliance. Instead of destroying the towers, Tamamo suggests that they use the generators to create a global seal that instead weakens holy energy using data on Heinrich's seal, removing the Angels’ immunities to non-holy attacks, along with distorting the barrier that protects the seal on Alice and the Heaven’s Gate’s physical form. However, all four generators must be interacted with simultaneously within a three second grace period, otherwise the swapped data will be overwritten and the exchange will fail.
All of the Four Heavenly Knights are assigned to the Four Towers to perform this task, but are intercepted by the Next Dolls. Each of the guardians are defeated, and by communicating through telepathy, the data exchange is successful.