Menace Beneath Lucis

The Sealed Doors are eight doors are encountered in the Menace Beneath Lucis sidequest. They are each locked and can only be opened with a key Ezma possesses.

Story
The doors were created and sealed a tremendous danger and evil behind each one of them at least thirty years before the events of Final Fantasy XV. According to Ezma, the doors were only a temporary solution and would eventually break. Knowing this, she waited patiently for someone she thought was capable of destroying the monsters behind the doors to entrust the key to in order to purge the monsters within each door.

Regis Lucis Caelum met Ezma during his journey thirty years before the events of the game, whom Ezma believed was capable of destroying the monsters and requested he take the monsters down. Due to the circumstances of his journey, Regis was unable to at the time, but promised he would take the task when the war with Niflheim was over. When Niflheim defeated Insomnia, this promise was thought to be lost, but Noctis would end up fulfilling this promise unknowningly.