The Baron
This level has no peculiarities within it whatsoever - at least none that we've yet discovered. However, the entire level is itself something of a novelty, being the first and only indoor level in all the Myth series. As you can see in the screenshot below, this is accomplished by simply making everything above "ceiling" level a solid black mesh, representing "the void" (the nothingness outside the visible level, which is normally a smeared mess if by some bug you are able to view beyond the mesh).
Addendum: Mark Basset wrote to Myther.com, "In the pregame pictures, look for the evil baron sitting at his desk writing. On the bookshelves behind him are a copy of Jaws, and another of Star Wars." Thanks to IronDuke for pointing this out.
Martel adds to this last one, mentioning that in a higher-res version of this same pic on page 107 of GURPS Myth, you can see many legible titles on the spines of the books. They are: Myth, Pornography, Satan's Cook Book, Oliver Twist, Dracula, Moby Dick, Frankenstein, Mein Kampf, and Frazetta. On the very top shelf you can also see a "tallica" visible on the bottom of one of the books; Metallica maybe? There are movies and video games in there, so why not music?
Written and compiled by Forrest.