UnderRealmSetting

I should note that this section partly reveals the inspiration and physical science of what i believe the caverns are the result of, which the inhabitants of the caves due to the lack of scientific thought, may have no idea about. In many places, liberties are taken with the science.

Geology

The UnderRealm is a series of caverns, tunnels that stretches for untold thousands of kilometers. Caverns vary considerably in size, the middle and most common size is about several kilometers in diameter, some can be considerably larger, whilst underhold caverns tend to be smaller expect for the main city chambers.

Many caverns are formed in limestone, but other rock types include chalk, dolomite, marble and salt. These are formed from slightly acidic fluid flows that slowly weather the rock.

The second most form of cavern and one that dominates in many areas, are lava caves. These are the result of long-drained lava flows and form tunnels and large caves with relatively smoother walls than that seen in solutional limestone caverns. The rock of these caverns in primarily granite, Gabbro and other itrusive igneous rocks.

A surprisingly common type of cavern is artificial, having being clearly cut from the native rock. Whilst the most famous of these are underholds, there are plenty of caverns that appear natural at first, but have clearly artificial origins if given closer scrutiny. Many of these caverns appear to be particularly suited to growing goop, fungi and mushrooms.

In addition, the most recent arrivals to the underrealm often fashion their own caverns and tunnels.

Flora and Fauna

Flora

Goop

The most basic form of life in the caverns is bacteria. Known as goop, the bacteria feeds on thousands of tiny fissures that leak warm mineral rich water located in many caverns of all types. It forms a thick biofilm of slime about 20 centimeters in thickness on average. The dominant form of bacteria is perfectly harmless to humanoids and its strong antibiotic action has effectively eliminated the competition in the caverns it is found. Goop is bio-luminescent and generally a light blue in color.

Goop is also the staple food source for humanoids, the top layer can be easily scrapped off every few weeks and mixed with basic plants to create a fairly palatable porridge.

Plants

Without access to sunlight, plants relies on the bacteria in order to fuel their cells. Plantlife has a symbotic relationship with the goop, helping to stabilize the biofilm and draw up water. Whilst having no leaves, they still have branches and stalks, often ending in fruity bulbs of organic matter.

Fauna

The animals of the underrealm are varied, from the relative innocuous cave mouse, to the venomous giant spiders and the creepy octopus.

Wyrm

A popular creature is the now household companion, the lesser Wyvern. The size of a dog, these leathery creatures have been described as lizard-like bats and have a similar appearence to mythic tales of 'dragons'. They often ::roost upsidedown in caverns and have a diet that includes giant spiders. Tamed for hundreds of years, many breeds exist.

Octopod

The Octopod is a bizzare creature with strong muscular tentacles and a bulbous head with a rubbery soft skull. They have suckers which attach well to cavern walls and two tentacles in particular have sharp claws suited to digging, which they use to build predatory hideouts from which they can lurk, waiting for unsuspecting prey.