Mystery: Holy Grail War

Among the remnants of the past who were put down by the Fool from the Source Castle, the occult knowledge they learned was integrated with the Holy Grail War system of the original earth-shaped moon, and was written in the novel. After the War of the Old Ones, the Holy Grail War will begin for the first time. This work is based on the fanfic of Lord of Mysteries, it's a joy to read.