From the Introduction:
The DIRGE RPG covers a lot of ground, but some things got left out in the effort to cover the basics. Your Pact may get into a car chase, or may encounter a wide variety of medieval or high-tech weapons out in the Pleroma. You may wish to play as one of the vicious, territorial, shapeshifting Enkidu, or one of the wretched Children of Darkness, or a member of one of the many minor Mystic Cult. You may just want more information on the conspiracies of the Hierates, looking for some faint glimmer of hope, some weakness in their monolithic structure. Except for that last bit, hope, you can find all of that here.