Lumen Histoire is located in a secret underground room in Fairy Tail's original building. This secret is only known by Fairy Tail's Guild Master and is passed on to the new Master successively. Precht showed it to Makarov when he became Master. Years later, Makarov showed it to Gildarts Clive when he told him that he wanted him to be next Master of Fairy Tail. According to Ivan Dreyar, Lumen Histoire is Fairy Tail's darkness, while according to Mavis Vermilion, it is Fairy Tail's light.
After Hades' soul is freed from the defeat of Franmalth he tells Natsu and Lucy that despite stopping Face its not over and Makarov needs to "release the light", when Makarov was told this information through Warren's telepathy he realized Hades was referring to Lumen Histoire.