The realm of the underworld, where the "escaping Gehenna" arc takes place. It's a reflection of Assiah at its fringes but only intersects with Assiah a little. it is its own separate dimension, though not one of direct physicality like Assiah is. It is a spiritual plane and those who are of Assian descent cannot exist there safely, unless they have demonic/otherwise supernatural blood in them. Demons are the residents of Gehenna, as well as anything sinful and in opposition to God.