Cover of Darkness is a mod for registered Wolfenstein, made by Liso1 & Mek. It was released on December 1, 2007.
All 60 levels were apparently based on an earlier set by Mek, Mek's Wolfenstein 3D. This particular set never made its way to the Wolfenstein 3D Dome, however.
Graphics are taken from ROTT and DOOM (via the Image World and various DOOM-inspired mods) and coding changes include new ceiling colors and increased health and ammo.