1 Monster (called 1 Monster Megawad in its text file) is a megawad released on October 24, 2007, featuring 25 maps created by 15 Doomworld community members. It requires a Boom-compatible source port to play. As the name implies, each map contains just one type of monster. A bug-fixed version was also released on October 29, but never uploaded to the /idgames archive. It is available on the Doomed Speed Demos Archive, with later additional fixes by Andy Olivera.
The project was conceived by Dr. Zin, who started the original Doomworld forums thread on December 27, 2005. While originally planned as "a megawad for 2006" with 32 maps, development turned out to be slower than expected. The project leaders, in order, were Doomworld forum users -_DLD_-, sausage, and Philip Brown (Liberation).
- Ryathaen. "Doomworld. 2007-10-29. Retrieved 2015-12-23. " at
- "Update 3/31/11: I've added a fix for MAP03; 100% Kills is always possible, now. Andy Olivera" (1monster_bugfix.txt in . Retrieved 2015-12-23.)