Caverns of Darkness

Caverns of Darkness is a 12-level mapset for Doom 2 by The Chaos Crew in 2002, using a custom source port, whose source code was recently released by Joel Murdoch, based on the Eternity Engine v3.29 called the "COD Engine". Because of the custom engine, or a DOS emulator such as  is required to play. The modification is well known for its liberal use of fake three-dimensional constructs using middle textures, and ambient sounds.

ZDoom patch
In 2008, Graf Zahl released a patch for Caverns of Darkness, allowing it to be played using ZDoom. It works by substituting DECORATE actors in place of the original hard-coded custom thing types and weapons, as well as using MAPINFO to use a custom map translator to account for the COD engine's new sector and linedef types.

Levels

 * MAP01: Surface by Christopher Lutz
 * MAP02: Six Feet Under by Christopher Lutz (exit to MAP11)
 * MAP03: Hell & High Water by Christopher Lutz
 * MAP04: Hydrosfear by NokturnuS
 * MAP05: Command Control by Emil Brundage (NaturalTvventy) (exit to MAP12)
 * MAP06: Periditions Abyss by Christopher Lutz
 * MAP07: Lava Processing by Christopher Lutz
 * MAP08: The Pit by Christopher Lutz
 * MAP09: Hellmine by NokturnuS
 * MAP10: Caverns of Darkness by Christopher Lutz
 * MAP11: Symbol of Grace by Christopher Lutz (secret map)
 * MAP12: The Stand by Christopher Lutz (secret map)