The God-Machine is a sentient, supernatural, extremely powerful and alien entity, similar to an occult supercomputer, with an interest in Earth. It is described as the Creator in The Testament of Marco Singe, the so-called "Pain Prophet" of New Delhi, although whether it is actually the Creator or not is impossible to prove. Singe was wrong on several counts, such as demons being creatures created from normal animals, when true demons are fallen angels, algorithms of the God-Machine who came to question their purpose and rebelled, losing their connection to it in the process.[1]
What is known is that it is fully deserving of the title, having long since passed the point where Clarke's Third Law ("any sufficiently advanced technology is indistinguishable from magic") applies, knowing of physics undreamed of to mortal scientists and with the capacity to use them. The only limit on its power is its need for an "occult matrix", an extremely precise supernatural manipulation of physical laws, reliant on Infrastructure, in order to work its miracles. Even mortals can disrupt a forming matrix, but the God-Machine feeds on its own growth; frequently, a complete occult matrix will summon a new angel into the world, who can oversee and construct more Infrastructure, which can complete more summoning matrices, ad infinitum.