You need the hexdd.wad file, which is usually found in the installation folder of Hexen: Deathkings of the Dark Citadel (available on Steam or GOG).
Unlike the base game, hexdd.wad assumes the player is already an expert. Resources like blue and green mana are scarce, and enemy density is dialed to the maximum. Monsters ambush the player from hidden walls, and traps are far more lethal, often utilizing instant-death crushing ceilings or bottomless pits. How to Play Hexdd.wad v1.1 Today
While technically an "IWAD" (Internal WAD), it still requires the original hexdd.wad v1.1
: The compilation omitted the critical SNDINFO lump . Without this data index, the engine could not map MIDI audio tracks to the expansion's new levels. Unless users played the game using a physical audio CD in their disc drive, the expansion was entirely silent.
Green and Blue mana are scarcer in the expansion hubs. Rely on your Class Weapon 1 (Fists, Axe, or Wand) whenever dealing with isolated enemies. You need the hexdd
Deathkings of the Dark Citadel consisted of 20 new single-player levels spread across three massive hubs:
The final descent into the Dark Citadel, featuring some of the most massive and intricate architecture seen in the id Tech 1 engine. Key Features of v1.1 Monsters ambush the player from hidden walls, and
This resulted in the game functioning perfectly, but with no background music playing during gameplay, creating an eerily quiet, atmospheric experience that wasn't intended by the developers. The Solution: HEXDD.WAD v1.1
You must fight your way out of this hellscape to claim the Chaos Sphere and truly purge the world of Korax’s lingering legacy. Gameplay Mechanics and Level Design
Here is why a veteran player or modder would specifically track down :