WadSmoosh

WadSmoosh is a tool for merging classic Doom games into a single IWAD file for GZDoom. It combines Ultimate Doom, Doom 2, Master Levels, No Rest for the Living, Final Doom, and Sigil, allowing you to play all official releases and user mods without relaunching the game. WadSmoosh is a command-line program that requires a one-time run and will create a PK3 file for ongoing use; it's suitable for users who own any combination of the Doom games.