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.
MCS is credited for the blocking object code, and Luke Strauman for wider music selection.
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.