Admin note: modern source ports will need md_hexen_fixed.wad to play Opulent's demo on this WAD (https://dsdarchive.com/files/demos/md_hexen/734/mdhx-422.zip) and possibly to run the WAD at all. Otherwise, the following error will be thrown:
  Required ACS script 250 not initialized

The fix applies is to add that script along with a bunch of others throwing the error with no script body to the BEHAVIOR lump. The fixed WAD contains a SCRIPTS lump with the source code for the BEHAVIOR lump. No other changes were applied. The fix WAD is authored by 4shockblast.