The last volume in the three volumes of the original Dungeons and Dragons rules covers, as the title says, the Underworld and Wilderness. With this the book means mainly the environments where the game is set, the Underworld being mainly about dungeons and dungeon construction while wilderness does the same for the outdoors.

However, the volume isn’t just about environment and setting, it’s also about movement, traps, the structure of turns and later on in the volume things for players to do during downtime, like the construction of castles, the hiring of Men-At-Arms and Specialists, upkeep costs and all those fun things which are very much marginal to the game itself.

Much as in previous volumes it depends heavily on the rules that Gygax had created for CHAINMAIL, his historical miniature battle game that was the direct ancestor of D&D. This is so much the case that throughout the volumes D&D feels almost like an add-on to CHAINMAIL rather than an independent game. However this would not be the case for much longer.