The Praetors of Orpheus are a Loyalist Second Founding Space Marines Chapter who are Successors of the Ultramarines. The Praetors of Orpheus' understanding of Imperial science and technology is second only to that of the Tech-priests of the Adeptus Mechanicus itself. Many believe that the two organisations are tied by more than shared service in the Emperor's name and that the Praetors have shared personnel and goals with the Mechanicus in the past. The large number of Praetors of Orpheus who undergo cybernetic augmentation with bionics would lend weight to this theory. The Praetors of Orpheus are currently active in the star systems neighbouring Pavonis.