This "Shadow of the Serpent Riders" edition includes the original three episodes plus two additional high-difficulty campaigns:
Download GZDoom and extract it into your game directory (often C:\GOG Games\Heretic Shadow of the Serpent Riders\base ). Heretic.Shadow.of.the.Serpent.Riders-GOG.rar
Grants the ability to fly, which is essential for reaching certain secret areas or navigating levels like "D'Sparil's Keep". This "Shadow of the Serpent Riders" edition includes
Run gzdoom.exe . It should automatically detect the HERETIC.WAD file and launch the game with modern features. Heretic.Shadow.of.the.Serpent.Riders-GOG.rar
Supercharges your weapons for 40 seconds. For example, the Hellstaff will rain fire from the sky, and the Phoenix Rod becomes a flamethrower.