Underground

ULTRA.WAD is not a valid WAD file. No PWAD signature, no valid WAD directory. After going through it with a hex editor and seeing strings like "Wolf1 Map5" it does seem like something for Wolf3D, not DOOM2.

Quite. This unzips into a 47k wad file but it's not Map01, or Map02, or Map03 or Map32 or Map31, and it's not E1M1 or E1M2... and it crashes XWE and Doombuilder. I'm not going to CLEV through all of Doom 2's levels to find out which one it is, assuming it works at all. And now I'm angry and annoyed, and I don't like that.

Where is the new level? Says it replaces d2 m01. But it does not.

Judging by the file header, which starts with TED5v1.0r, this is probably not a Doom map at all, it could be for Wolfenstein 3D or Rise of the Triad. The readme mentions under.wad, which is id=7942 and is present and correct, whereas the zipfile contains a file called ultra.wad, which doesn't work in Doom or XWE etc as noted above. Weird.

its ok