15 Master Levels is a mod for registered Wolfenstein, made by Ipank7000. It was released on January 29, 2012.
As the title indicates, the mod features 15 levels, of which 3 are secret levels. No new graphics are featured, but the SDL EXE features new ceiling colors, a fifth difficulty setting and a handful of other changes.
The level of difficulty is quite high, evidenced by the opening level. This level, along with a handful of other levels, was taken from Ipank7000's Mapset.