Dark colored; sooty; murky; obscure.
For example, Hubert's photograph of Bruno's broken key, where it was captured whole, with the handle intact. This shot comes from the most unanticipable place. An incredible story to tell. Even Hubert and I are running out of ideas for possible explanations. There are also other fuliginous and uninterpretable things going on at that place. (Context: The key found ingrown in a treetop is broken and missing its bow. However, an unexplainable eerie glowing appearance in the city cemetery shows both parts of the key together. Source: J∙ Okram - The Mystery of the Rammed Key.)