INTRODUCTION WHAT IS THE UNDERDARK LIKE? The Underdark is the vast realm of interconnected To understand the Underdark, we must first caverns, passages, and tunnels, found far beneath understand real world caves. And to understand the surface of the earth. It is a place of no sun, no caves, we need to know how they are made. rain, and no change of seasons. It is, in fact, an almost timeless place, with any changes marked on a Cave Creation geological scale. That said, the Underdark is alive, in In the real world, most caves are created from the its own way. The slow drip of water “grows” limestone erosion of limestone, chalk, gypsum, and similar features, or wears solid stone away. Fungi grow in minerals. Rain water soaks into the ground, seeps place of grass, trees, and crops, while creatures of all into a seam of porous rock, and dissolves it, leaving types, many uniquely adapted to life underground, eat a cavity. This simple process is responsible for some both the fungi and each other. But more dangerous of the most dramatic and dynamic caves on Earth, yet are the civilizations that dwell and thrive in the such as Carlsbad Caverns, Mammoth Cave (the Underdark. The most benevolent of these are the longest cave system in the world), New Athos Cave dwarves, but there are also drow, kuo-toa, mind (the second largest cave in the world), Son Đoong flayers… and such aberrant denizens as aboleth and Cave (the largest cave in the world), and others. In beholders. Simply put, the Underdark is not to be addition, the dissolved limestone will eventually taken… lightly. leach out of the water, forming dramatic formations, such as stalagmites, stalactites, columns of solid HOW TO USE THIS PRODUCT stone, flowing masses of “drapery,” and ribbons of “bacon.” However, caves such as this can only form You can use the content found in Underdark where there is sufficient water. In arid areas, different Discoveries in several ways. For starters, it provides methods are required. you with numerous encounters you can use whenever your players ever enter the Underdark. Or, you can In areas where there is no water, the air itself can use the listed encounters to add some variety to more create caves. Strong winds can carry dust, sand, and mundane caves, lairs, mines, and tunnel systems. You gravel with it, slowly grinding a cave out of areas of should also feel free to adjust, alter, and expand upon softer rock (such as sandstone). Volcanic activity can each encounter as you see fit, tailoring each one to create what are called “lava tubes.” As molten rock your specific campaign world. Oh, and don’t always flows along, the outer surface will cool, while the depend on the dice. If you see a result you like on a liquid stone inside keeps going. These tubes can be table, use it, don’t worry about rolling for the result. It very long, with one in Hawai’i measuring more than is your game. Make the most of it. 40 miles in length. Glaciers can create similar caves, through the melting of ice within the glacier. As the As a final note, anything in bold refers to a stat water seeks an escape, it will work it way through the block in either the Monster Manual or Volo’s Guide to ice, washing out long passages. Monsters. Flowing water, washing along a slurry of stone and gravel, can create caves as well, even through the hardest of rock. The washing and grinding out of Gandalf: There are older and fouler things than Orcs softer stone can create what are known as “fracture in the deep places of the world. caves,” when the surrounding rock collapses. Finally, - The Fellowship of the Ring talus caves are the result of a rockfall, usually at the base of a cliff, and are usually made from unstable piles of stone. SampleIn the Underdark (and otherfile fantasy realms), caves and cave systems may be created artificially. 3 while fire elementals may be able to melt rock away. Tunneling creatures, such as ankhegs, umber hulks, and purple worms, can leave large passages, similar to lava tubes. Magic can be used to create caverns and cave-like structures, with such spells as stone shape and transmute rock. Finally, it is possible, especially in areas of strong or unstable magic, for the ground to shape itself into cave-like structures. Cave Formations As water in a cave flows along and evaporates, it leaves behind layers of minerals, which — over long periods of time, can form structures. These are known as speleothems (from the Greek spēlaion, meaning “cave” and théma, meaning “deposit”). Built up over hundreds and thousands of years, these structures come in a wide variety of shapes and sizes. A short list of cave formations is as follows: Dripstone: As the name indicates, dripping water creates these formations. Dripstone accumulations tend to be vertical and can often result in thick columns. • Stalactites are roughly cone- shaped structures that hang from ceilings. In the Underdark, piercers like to hide among The gods themselves may create caverns, perhaps stalactites. In addition, some through physical manifestations of their divine Underdark stalactites are immense, allowing them form or through the expression of their divine will. to be hollowed out and used as living quarters. Elementals may form caves as well. Earth elementals • Chandeliers are chaotic collections of stalactites can simply glide through stone, but many other that can form very complex structures. Dwarves beings fromSample the Elemental Plane of Earth can bore and deep gnomes may carefullyfile guide the growth through earth and rock with ease. Wind elements can of chandeliers to produce elaborately beautiful blast out holes, water elements can wash them out, creations. 4 • Helictites consist of a central stalk festooned Flowstone is akin to dripstone, but grows to look with gravity-defying branches, spirals, and twig- more like hanging curtains or sheets. like projections. They include formations with • Draperies, also known as curtains, hang from the such descriptive names as: butterflies, clumps ceiling and have a thin and wavy appearance. In the of worms, curly-fries, hands, ribbons, rods, and Underdark, draperies may become thick enough saws. As with chandeliers, dwarves and deep to serve dividers in a cave, forming rooms with gnomes may cultivate helictites the way a wood rippling walls. elf might guide the growth of a tree. • Bacon is a form of drapery that contains colored • Ribbons are stalactites that come in long strips bands. In Underdark areas of wild and unstable and greatly resemble their name. magic, it might even be edible. • Soda Straws are long and thin, with a cylindrical • Rimstone, also known as gours, is a flowstone shape, as opposed to the cone shape of regular buildup in cave pools. It often looks like semi- stalactites. As most fantasy campaigns don’t circular stairs, and may form large multi-level feature drinking straws, you may want to call terraces. As rimstone occurs in cave pools and them ‘grass stems’ instead. streams, it may create dams, leading to water-filled • Stalagmites are roughly cone-shaped structures that terraces. stand upright on the cavern floor. In the Underdark, • Stone Waterfalls are flowstone formations that ropers appear almost identical to stalagmites when look like river cataracts frozen in stone. In the their eyes and mouths are closed and they aren’t Underdark, these formation may actually be ancient moving. As with stalactites, Underdark stalagmites rivers turned to stone through the acts of the gods, can become large enough to be turned into guard elementals, or strong magic. posts, watch towers, and living quarters. • Broomsticks are vertically akin to soda straws, in Cave Crystals are formation of minerals in a that they are tall and thin. crystalline matrix. Normally, these structures are fairly small, although there is the Cave of the Crystals • Fried Eggs often look just like their name sake — in Mexico with gigantic crystal formations up to 40 they have a smooth rounded center and a rougher feet in length and weighing 50 tons or more. In the outer border. Underdark, similar crystals could easily be 400 feet in • Totem Poles are tall structures with segments, length (or even longer). showing the stalagmite’s various stages of growth. In the Underdark, these may server as markers, • Anthodites are clusters of needle-like crystals guide posts, and indicators of borders. radiating out from a central point (much like a flower). Often found on the ceiling of caves, • Columns occur when stalactites and a stalagmites individual needles may grow to be around three feet meet, or when a stalactite grows long enough to in length. The Cave of Swords, found in Mexico, reach the floor of a cave. Given enough time, a contains similar crystals up to six feet in length. column may become large enough to wall off a section of a cave. In the Underdark, truly immense • Dogtooth Spars are large crystals that grow to columns can become the equivalent of apartment resemble a dog’s teeth. They often appear in clumps, buildings. Usually the core is hollowed out to near flowing water. When appearing in dense contain a stairwell, then living spaces are carved out patches, dogtooth looks much like mounds of snow. of the rock, radiating out from the stairs. • Frostwork consists of growths of crystal with a feathery appearance. As the name indicates, it looks very much like frozen water. Can’t recall which is which between stalactites and • Moonmilk is comprised off limestone runoff. It is a stalagmites?Sample Just remember the following: c is for white in color, with a creamyfile consistency.