The Deep Hollows is the world underneath the surface of Celesia. It is the common name of the vast network of tunnels and caverns woven throughout the underground of the planet's crust. It was formed by the magic of creation, expanded by the tunneling of a myriad of creatures. It is an ecology all onto its own. It is home to the dark elves, the deep gnomes, and so many other creatures and races. Entire nations can be found, along with untold horrors and dangers.
Celesia's oceanic crust is 5 to 15 miles thick, while its continental crust is 30 to 60 miles thick.
Alternatively called the 'Deeps' or the 'Hollows'.
Layers
The Deep Hollows are divided into 3 distinct layers.
Upper
Home to dwarves, orcs, kobolds.
Closest layer to the surface, only present on continents.
Composed mainly of tight tunnels and caverns with an average size of a family home. The largest caverns are about city-size, and generally found under mountain ranges.
Water sources from rivers, rain, and oceans.
Lava sources are generally only found around volcanoes.
Temperature and humidity is one step higher than the surface.
Mid
Home to dark elves, grey dwarves, deep gnomes, troglodytes, sserassin, tharaxin.
Like the upper layer, the mid layer is limited by the continent.
City-size caverns are far more common connected by highway-size tunnels. Some of the largest caverns can extend to dozens of miles in diameter, supported by enormous stone columns.
Water sources from rivers from the upper layer and from the oceans. Real lakes and small seas, with highway rivers, can form on this layer.
Lava sources are more common, forming small rivers.
Low-level harmful radiation is present, but can be adapted to. Its effects can be counteracted with strong constitution, and medecines sourced from the local ecology.
The environment is very humid, resulting in general very hot temperatures.
Lower
Home of thul-koon, many aberrations.
The lower layer can exist below the ocean floor.
Caverns can extend to over hundreds of miles of unbroken vastness, supported by massive columns miles in diameter.
Water sources from the mid layer and from the oceans above. Large seas can form on this layer.
Lava is present in equal amounts to water. Large, flowing rivers and vast lakes of magma are common.
High-level harmful radiation is present. It can only be countered by magic or natural immunities.
Areas close to the ocean are extremely humid, while other areas are very dry. The temperature is generally considered to be severe heat. Creatures without fire resistance or immunities suffer fire damage from exposure.
Ecology
Life and civilization are only possible thanks to the unique, and almost alien, flora, funga, and fauna native to the Deeps. Most life originates from streams of water that seep into the Hollows, carrying many organisms that settle in otherwise barren underground crevices. These organisms eventually evolved to adapt to subterranean life, although the presence of water, geothermal heat, and ambient radiation are often necessary.
Much of the Deep Hollows' vegetation, fungi, and creatures have developed bioluminescent abilities. Depending on the variety of lifeform, this light serves to attract mates, warn off predators, camouflage, lure prey, and attract creature to help spread their seed or other elements. Naturally, the denizens of the Deep Hollows have domesticated many of these lifeforms to provide light in the lands below.
Fauna
Rockworm
The rockworm is a giant worm that is vital to the ongoing ecology of the Deep Hollows. While a true omnivore, the rockworm subsists primarily on rocks. Many of the tunnels of the Deep Hollows are the result of these worms digging and feeding through the stony masses. However, the true gift of the rockworm is its refuse that it leaves in its trail. Rockworm waste is rich in nutrients perfect to grow plants and fungi. In addition to this valuable resource in the barren underground, rockworms often eject ores and gems. While they are able to digest these elements, their diet does not generally require the amount that they inevitably consume, resulting in the excess becoming freely available for anyone who comes across them. Finally, rockworm meat is edible, and the creature is a food source for other subterranean creatures.
Rockworms continue to grow and grow over time, and it is unknown if their lifespan actually has an end. The more they grow, the deeper they descend into the Hollows. Upper rockworms have an average length of 10 feet with a girth of 2 feet. On the mid layer, rockworms typically reach around 40 to 60 feet in length with a girth around 10 feet. On the lower layer, rockworms are almost never below 150 feet in length and 30 feet in girth. Legends tell of rockworms reaching lengths of over a 1,000 feet and over a 100 feet in girth.
Rockworms are hermaphrodites, and are capable of reproducing without a partner, although doing so increases the chance of successful reproduction and an increase in spawn. Regardless of size, rockworms dig upwards to the upper layer to lay their clutch of cocoons. The larger the rockworm is, the rarer it reproduces, but the occasional colossal rockworm birthing is feared by many, both beneath and above the surface. Their instinctual drive to tunnel from the lowest depths of the Hollows to the upper layer bears the impact of a terrible earthquake.
Flora
Glow Moss
One of the most common plantlife in the Deep Hollows.
Has adapted to no longer need sunlight, and generally has a white or clear colouring.
Subsists primarily on moisture, the natural gases in the air of the Hollows, and some variety feed of the natural ambient radiation.
Glows between green and blue.
Funga
Deep Hollows funga have adapted to thrive without an external light source. Like funga on the surface, Deep funga come in a multitude of varieties, equally poisonous and edible. Fungi are a staple in Deep denizen diets, as well as their poisons and alchemical concoctions.
Giant Cave Fungus
The common giant cave fungus grows in areas of rich nutrients and organic matter. Given the space, its mushroom stalks can keep growing indefinitely.
The stalks glow blue to purple light.
The stalks are not edible, but are as strong as wood. Deep denizens now harvest this fungus to produce building materials. Additional alchemical treatment can increase the fungal lumber's strength and durability.