Issulon is one of the twin Cathedral Moons preserving Cata-Zin ruins studied by the Thinderin and Humanity. The other moon is called Eduoma. The Cathedral Moons orbit Hequidar I at a distance of roughly one AU from the sun and are of artificial origin. Issulon is the outer moon and is believed to have been constructed much later than its twin, perhaps in mockery or opposition to it. It is also called the dark cathedral and has an abnormally low density. The dark cathedral is a terrible place. In the harsh vacuum of space towers of artfully sculptured rock cast sinister shadows across brooding canyons of igneous origin. Whole mountain ranges have been carved into disconcerting abstract and semi-abstract forms. Under the weak gravity, brittle microcrystalline minerals can soar in twisted arches and vast bridges over ranks of patient statues and shiny sheets of mirror cold ice. There are many who say that Issulon is haunted by twin spirits of extinction and fear. This is the doorway to the Congress of Shadows, a centre of power where for the first time in nine million years ancient energies are flickering in alien machines. Ramon Avva, the void priest, stands on the threshold, hesitating. [The background structures, glimpsed within the Congress of Shadows are as credited. The relief on the doorways is my own modeling, representing the Anti-Syradell symbol and built in photoshop then turned into a terrain]