Teratan Tunnels Geographic Location in Yonderverse | World Anvil

Teratan Tunnels

The Teratan Tunnels are a series of caves and caverns found deep below the surface of Xiskin. These cave networks are home to an abundance of life, including the infamous twattels. The Teratan Tunnels are laced with precious minerals and gems, commonly ambercite which is used in crafting explosives.

Geography, Location & Climate

The largest cave network system on Xiskin, the Teratan Tunnels stretch a hundred miles round Exxhian, a small island continent.

There are seventeen entrances to this network, found all across the island, emerging from the arinite rock.

The tunnels are difficult to traverse; jagged walls, tight corners, and thin corridors make navigation tricky.

Teratan Tunnels by Mochi

The caverns themselves range greatly in size. The largest cavern's roof stands seventy metres from the cave's floor at its highest, and reaching a mile in length before diverting into thinner tunnels and crevices, no wider than a rat's tail.


Since there are no native sophonts on Xiskin, the first people to explore the Teratan Tunnels were from another planet. The oanie were the first to come across these sprawling caverns, mining several Mink: Cargo spacecraft's worth of arinite, ambercite, and an assortment of flora and fauna.

Surprisingly, the oanie did not claim the planet as their own. Theories have grown and spread as to why, but the answer remains unknown. Instead, Xiskin was taken control by Maresa, a planet that rescues others in need, Xiskin being one of them. The tunnels were not explored by Maresans, but the first spacecrafts landed close to several entrances, and a colony of twattels fled into the vehicles, were transferred to Maresa, and formed an invasive population.


Twattel by Mochi

Some species in the deepest parts of the Teratan Tunnels have been isolated from the surface for millions of years, forcing adaptations and evolutions. These organisms have adjusted to a subterranean lifestyle, many major physiologies altering to better suit their environment. Many animals have gone blind, such as twattels, who rely on echolocation.

Many plant species rely on phosphomancy to photosynthesise. Their chloroplasts are adjusted to take in light magic, as opposed to solar energy.

Cave System
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Inhabiting Species
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Dec 28, 2023 13:53 by Dr Emily Vair-Turnbull

Scary cave system. :O The idea of tunnels as thin as a rat tail gives me the heebies.

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