Gutwood
The Gutwood is a large area in Thorgh's interior which seems to be largely filled with strange organs and ducts supporting a complex ecosystem of dependent life forms. The profusion of organs, many sprouting from the ground like trees, and the proliferation of other life make the Gutwood somewhat reminiscent of a forest or jungle, hence the name. Although it's widely presumed that the Gutwood has some purpose in Thorgh's anatomy, no one has yet been able to determine exactly what that purpose is. Certainly the harvesting of parts and materials from the Gutwood doesn't seem to have harmed the living world, so evidently there's some redundancy in its design.
The Gutwood lies some eighteen kilometers below the world's surface, though it is not all at the same level and slopes down significantly but irregularly from north to south. Spanning dozens of enormous chambers joined together by wide ducts and apertures—as well as many smaller chambers—, the Gutwood covers a roughly reniform area a little over three million square kilometers in area. This, in fact, describes only its outward dimensions; apparently Thorgh's space-curving abilities have been applied to induce a multum in parvo effect on at least some of the Gutwood's chambers, making it larger internally than its external dimensions would imply. Most of the Gutwood has never been formally explored or mapped, and its true interior area remains unknown, though there is reason to believe it's at least a factor of three or four larger than the area it externally occupies, and possibly much more than that. There are some rumors that the depths of the Gutwood contain permanent wormholes leading to like areas in other living worlds similar to Thorgh, but there's no conclusive evidence of this.
Contents
Whether the organic masses and protrusions that fill the Gutwood are really literal organs of Thorgh is dubious, but "organs" remains what they're typically called. These organs come in huge varieties. Hollow tubes of tissue reach from the Gutwood's floor to its ceiling hundreds of meters above, many of them branching, some of them filled with various fluids and some containing only air. Branching fans of fronds like exposed gills proliferate, among the forest's other "foliage" looking vaguely reminiscent of ferns. Bulging sacs and bunches of connected sacs dangle from chitinous poles or hang from the ceiling or from the Gutwood's other organs, occasionally spewing liquids on their surroundings. Great "trees" of bone, flesh, and sinew branch to end in feathers, cilia, eyes, or other oddities.
Not all of the Gutwood's organs are sessile and harmless. The gill-ferns and even some of the smaller thewtrees may sway gently, with or without any sort of wind. Tendrils may grasp at passing entities, though only to hold them briefly and release them without doing obvious damage. In some places, spiky arches and spires occasionally gnash together like giant jaws. Some of the organs have unusual effects on certain living things: some flower-like growths called shellblooms cause the skin of humans and some other races to grow thick and hard to the point of immobility; an organ called a funball shaped like an orb on a stalk causes hallucinations in most intelligent species, and a flattened organ called a bagmouth somewhat resembling a disembodied segment of a colon seems to behave similarly to Thorgh's well-known interfaces.
The Gutwood is far from uniform; different kinds of organs may predominate in different parts. This is true not only of the thewtrees and other large "flora", but also of other features of the wood. In some areas of the Gutwood, the ground is what appears to be bare muscle tissue; in others it is covered with shell, with hair, or with writhing tentacles. Various streams and lakes mottle the Gutwood, some mostly of water (with many added chemicals, but still potable, though odd-tasting), others of acid or other exotic secretions. The organs of the Gutwood are, of course, unharmed by these fluids, but much of the life in the Gutwood has also apparently developed a tolerance for it; there are entire ecosystems, for instance, of acidic bogs, various organisms thriving where corrosive liquids lie a meter or more deep.
Unlike most of Thorgh's interior, much (though not all) of the Gutwood undergoes a regular cycle of light and darkness. This is not because of exposure to any sun, of course, but due to some of the Gutwood's organs; common in the Gutwood are glowing spherical growths called moonballs that periodically cover and uncover themselves like closing and opening eyes. While moonballs in an area have similar cycles, this may not be true of those farther apart, so that different parts of the Gutwood may experience "day" and "night" at different times.
Life
Like a conventional forest, the Gutwood supports a variety of life. The organs that are a part of Thorgh are supplemented by more conventional flora—while the gutwood has very few actual trees, the copious organs leaving little space for them, it does have its share of smaller plants and other flora, particularly saprophytes and other parasitic flora. Among Tellurian flora, fungi are particularly common, growing on and feeding off of the fleshy organs, especially shelf fungi, Wikipedia:puffballs, and various kinds of mold.
If the Gutwood's nonorgan flora are somewhat unremarkable, however, the same cannot be said of its fauna. Many of the fauna found elsewhere in Thorgh have adapted to the Gutwood; lutotes, sutsia, and starsnakes are all relatively common there, and smaller prey species such as rodents and their ecological analogues more so. Other fauna are unique to the Gutwood. Pitbacks store the Gutwood's acidic secretions in dorsal cavities for later use against opponents. Foolstrees use their resemblance to the Gutwood's common thewtrees to waylay ravin. Aleyas float between the organs' branches, providing feeble light even when the moonballs are dark (or where they're absent).
Although only very small areas of the Gutwood have been settled with anything approaching cities, and those near the edges, the inner parts of the Gutwood are not without ellogous inhabitants. Humans and members of other races roam the Gutwood as hunters and gatherers, living in loose tribal communities. Though their origins aren't certain, it seems likely that they are the descendants of refugees from civilization who long ago became lost in the Gutwood, or perhaps fled there from some persecution. In any case, the tribes of the Gutwood have existed for long enough now to have their own firmly entrenched cultures and traditions, which vary widely across different tribes: the Gutwood is more than large enough to support many diverse societies. There are also stories of an ellogous race apparently unique to the Gutwood, the varta. While they were long thought to be a myth, recent evidence seems to show that the varta do really exist, though still very little is known about them.
Resources
While the Gutwood has a not wholly undeserved reputation as a dangerous place to tread, there are some things in it that make some daring individual decide that venturing within is worth their while. Some of this is purely for the sake of finding things out; intrepid explorers might like to make names for themselves scouting the Gutwood's mysteries; biologists may find some of its life fascinating, and anthropologists might covet interviews with its tribal peoples. But the Gutwood also gives more tangible rewards for the well prepared (and fortunate) visitor.
Many of the organs of the Gutwood provide parts that can be harvested and processed (or in some cases simply used as-is) for culinary, cosmetic, or medicinal purposes. To give just a few examples, the orbfruit, found dangling from some of the forest's tendinous "vines", has a very sweet, slightly sour taste and a soft, not unpleasantly grainy texture, though its close resemblance to an oversized human eye makes some humans uncomfortable with it. Certain red excrescences found on the ground in areas of the Gutwood emit a powdery substance called seardust that on contact with the skin produces in many species a burning, tingling sensation often found erotic; despite there being no evidence of addictive properties, seardust is classified as an illegal drug in many areas of Thorgh. A slimy substance exuded by tendrils dangling from some of the Gutwood's thewtrees has been found to be an extremely effective treatment for blue mange, a dangerous disease afflicting juvel trees.
There are more exotic exports from the Gutwood, as well. Some of the Gutwood's fauna are valued as pets, such as the tiny, colorful dodin. Certain organs end in tiny bulbs called quabbies that have proven useful in some technological applications. Perhaps the most disturbing export is a faunum called a tacer, resembling something between a slug and a rat, which under certain circumstances has the ability to control the actions of humans and several other races. Properly treated, the tacer can be induced to merge with another life form in a mutualistic relationship, allowing its host to control its minions. In essence, an individual with a tacer symbiont can enthrall dozens of other individuals as their unwilling slaves.
Notable sites
While most of the Gutwood remains uncharted and wide regions are not known to have ever been entered by civilized beings, there are a few locations in the Gutwood that have attracted attention. The Rainbow Fountains is the closest thing the Gutwood has to a tourist attraction, a site where numerous vents in the ground frequently expel jets of brightly colored fluid. Gut Mountain is a gigantic fleshy cone that stands near the southeastern part of the Gutwood, less notable for its particular contents than it is for its use as a convenient landmark. The Woodsheart is an enormous organ which bears some superficial resemblance to a beating human heart. The Wrestlewood is a part of the Gutwood in which all of the organs are for some reason in constant violent motion.
There are also some significant features not confined to a specific location within the Gutwood but running through it for extended distances. The Gutwood's rivers among these, and the major ones are given their own names; the largest river of the Gutwood, is the Thinblood, which gets its name from its slight reddish tint (though it actually doesn't seem to contain anything similar to blood). Other such features include the Bowels, enormous tubes that run more or less horizontally through the Gutwood and can be used for relatively rapid travel (though the Bowels have dangers of their own), and the so-called Catchers' Road, a long, narrow area relatively free of the dense organs that fill most of the Gutwood but overgrown in patches with tiny hook-like growths (the eponymous catchers).