The world created is very vivid and somehow believable, but there’s so much mythology presented in the story with little to no explanation as to how that mythology works that it can be confusing. How does the Secularist function? Do his tattoos and markings change with his mood? When he feels honorable and just do they disappear completely? I suppose some can be inferred, but a bit of explanation or at least a view into the Secularist’s mind would have been helpful. Also, what exactly is the devil? These are questions that I’m sure any fantasy writer loves to hear, but they still need answering! Given these questions, it seems this piece would be much, much longer to satisfy even half of the questions that this story presents.
From a story standpoint, the change from beginning to end is very sharp and predictable (not that that’s bad). We don’t learn much about the characters, and the Secularist at times seems robotic (I likened him to the giant guy at the end of Prometheus). Given that so much of the story is dedicated to creating a colorful and exciting world for the reader, there is a considerable lack of action. Consider this for revision.