Zugnaex

The Name
Zona Pugna Exitium, or Zugnaex for short, are Latin words meaning Zone Battle Doom. It's classic FPS gameplay with a unique multiplayer experience.
The Story
In ancient times, a powerful demon, known only by the forbidden name Zugnaex, was imprisoned by forgotten gods to prevent the destruction of reality itself. The prison, an interdimensional cage bound by immortal blood, is impenetrable, indestructible... and smells really bad. However, the gods did not realize there is one way the demon can escape. If any mortal speaks its name perfectly, every single little tiny syllable, the demon will tear through dimensions, bypass its eternal prison, and return to annihilate humankind. It’s game over and humanity is out of quarters. But Zugnaex has never faced a foe like you. Only you and your friends can defeat the demon Zugnaex and save humanity. It’s global warfare on an epic scale to save the human race. Will you join us?
The Battles
The online service hosts many battle variations. Here are some that you can experience:

A Demon a Day - Work together with your friends to defeat demons. Each kill counts for all active players but be careful as friendly fire is enabled. Help each other to get the highest score and become a demon slaying legend.

That Guy - Complete different mission objectives with your friends but there's a twist. The demons are powerful and the marines may succumb to their will. Who is your ally and who is your enemy? Play to find out.

Pennies from hell - Demons drop pennies and you collect them. It's a PvP party where the best players will wallow in the riches offered by the denizen of hell.

Ready or Knot - It's time to play hide & seek but old school FPS style. It's PvP where all players are against "it." If "it" survives the other players explode just like in the movie.

Heir I Come - A new heir must be chosen. Who is it? Who is not it? And who are you? Survive the ritual and outlive everyone else in this twisted sequel to Ready or Knot. Side effects include paranoia, betrayal, and spontaneous dismemberment.

And many more including speed running, co-op adventures and the ultimate confrontation with Zugnaex itself.
The Source Code
Some of it was written by me. Most of it was written by you. You can use all of it to make something amazing yourself! Use the included source code to build your own battles.
zugzug.zip - This is the source code for zugnaex (the client) and zugsrv (the server). See the README file for instructions on how to build. (License: GPLv2)
zugbats.zip - This is the source code for a battle service with example battle modes you can run on your PC. In "Kneed Time," you need to finish a random UV E1 map in par. In "Kneed Help," you and your friends must 100% 2 random UV E1 maps before time runs out. See the README file for instructions on how to setup and run the battles. (License: MIT)
zugnite.zip - This is the source code for a companion launcher for Zugnaex that enables Steam achievements and authentication. (License: MIT-0)
zugdiff.zip - This is the source code for a utility used to patch game data files to maintain network compatibility. (License: MIT-0)
See source files for setup, build, and licensing details.
Important! Please read
Zugnaex is an unofficial client. This game comes with no playable content. To play or battle, DOOM and DOOM II must be licensed and installed on your PC.
Photosensitive Warning: This game and its downloadable content have flashing lights and visual patterns that could trigger seizures, discomfort or nausea in players. Please take appropriate precautions.
Region Restrictions: To provide the online service, we host servers in North America and Europe. Players in some regions may not be able to connect or may have slower network speeds. In addition, our application has very limited localization support. The English language is the only officially supported language for the game.