doom-complete.pk3 includes a TEXTURES lump that tells GZDoom: “When playing a Plutonia map, use THESE skies; when playing a Doom 2 map, use THESE.” It also resolves conflicts—for example, if Doom 2 and Plutonia both have an object named VILE (the Arch-Vile), the script prioritizes the correct version for the current episode.
There are three ways to load the file. Use Method A for the easiest setup. doom-complete.pk3
This occurs if your doom-complete.pk3 version is outdated relative to your GZDoom version. Solution: Update both the .pk3 and GZDoom to the latest stable releases. doom-complete