Stone Age: Before 1E 0
Copper Age: 1E 1-1E 2200
Bronze Age: 1E 2200-1E 4400
Iron Age: 2E 0-2E 700
Ancient Age: 2E 700-2E 2200
Middle Ages: 3E 0-3E 2050
Early Modern Age: 3E 2050-3E 2600
Industrial Age: 3E 2600-3E 2700
Machine Age: 3E 2700-3E 2800
Atomic Age: 3E 2800-3E 2850
Space Age: 3E 2850-3E 2875
Information Age: 3E 2875-3E 2900
Genetic Age: 3E 2950-3E 3000
Awakening Age: 3E 3000-3E 3415
Shattering Age: 4E 0-4E 250
Arynietu Frozen Land is an underground frozen water reserve located within the depths of the  landmass of Taerel. Records indicate that zu'aan were aware of the presence of these frozen caverns as far back as the Iron Age, though occupancy of the region only dates back as far as the Ancient Age. Historic evidence suggests that following the Satmor War between the Fiuq and Palss'nir Clans, small zu'aan communities that were caught up between the conflict in this region of Taerel decided to flee to the the underground icy caverns, which were known locally and avoided by most. Due to the large timespan of the surface conflicts between the two clans, it is thought that these zu'aan formed communities linked to the region that were willing to stay there after the conflict was over.
Large destruction of surface settlements is also a factor that is thought to have contributed to zu'aan remaining in the region, as many of them had no homes to go back to. As of the end of the Ancient Age, the zu'aan communities in Arynietu were formally recognized as a nation and have remained as such until the kin'toni outbreak. As a very hostile region, Arynietu's popularity is no doubt solely due to the Satmor War. Before war times ensued, the zu'aan of the region, which is a division between other regions, were vaguely aware of the caves, as multiple texts from this time period reference a web of interconnected ice cave network beneath the ground. Some of these entrances were even made public prior to the major conflict, and some of them were sealed off and made innacessible.
Though depictions of the caverns in written documents is rare, one can surmise from what little is there written about them that they did not possess any appeal that made it so the locals had the desire to explore them. In other words, there were no resources present in them that made it worth it to explore them. They were dangerous, unknown caves that were leagues below the temperature of the surface, dark and difficult to navigate, and nothing more than a death trap for explorers and curious or lost souls. They remained like that until the war. According to documents of the time, the idea of moving underground was first met with unrest from the local zu'aan population.
It is believed that the first settlers were those among the zu'aan that were to be drafted to the front lines of the war by the government, and feared losing their lives. In order to escape the draft and protect their families, they are thought to have been the first zu'aan to hide underground, presumably for what they assumed would be a short and temporary amount of time, as wars never lasted for too long. It is theorized that they found solace in the caverns and were, to their surprise, able to thrive, and over time they convinced their families, friends, and other villagers to hide down there with them. Despite the hostile appearance, a surprisingly good environment is the only explanation for as to why the initial civil unrest turned to stupefaction and later mass migration.
In any case, regardless of the truth hidden in the past, their civilization did thrive and remain underneath the ground, though it also moved partly over it following the war. As of the kin'toni outbreak, however, the need to hide among the icy caverns would understandably return, and the people of Arynietu would find themselves following after their ancestors and hiding among the sprawling cold caves in hopes of evading their new invaders. History repeats itself.
Arynietu is an underground region formely consistent of a natural water reservoir. It is believed that a great earthquake took place before zu'aan civilization started which caused local, currenly inactive volcanos to erupt and thaw the natural ice reserves in the region, flooding the earth and creating the underground reservoir. It is also believed that further on, once these volcanos cooled down, the thawed water begun freezing once again, and the sudden process caused most of it to assimilate onto the ground, creating large pockets of empty air. These pockets would later come to be known as the sprawling underground cave network of Arynietu.
Despite being called a cave network, it is important to mention that there are many locations within the caverns in which the ceiling opens to a certain degree, and that unlike natural caves found all over the world, there are more akin to artificial structures at a glance, being made of smooth stone and very large cavities. Furthermore, they occupy a very large amount of space, a total of 2,400 square kilometers. A small size when put relative to the size of Taerel, but a very large territory when compared to other cave networks. Much of this area is comprised of undiscovered, nearly impossible to navigate narrow tunnels, but there are also many open cavities that are thought to once have been filled with water.
The lowest point of civilization in the cave network is at an average depth of 568 meters. The highest point is at 20 meters. As expected, the climate within the caves is very odd, and very cold. The atmosphere is very humid, and mild winds are common within the caverns, especially near large openings to the surface. Precipitation comes in the form of leftover rainwater from the surface, which trickles down the caverns and inevitably freezes on the ground or on the walls. The walls, floor and ceiling are all covered in a thin layer of ice, hence the name of the region, and navigation within is perilous and very dangerous. The ground is, as expected, uneven in most places, but the walls and ceiling are composed of smooth rock at some of the larger basins, a likely effect of the previous water within.
The rock is very soft in the region, and very susceptible to erosion. If it weren't for the cold climate and layers of ice holding up the rock, it would likely collapse. In fact, the main risk factor within the caverns it that; rock falls. Heat is necessary for zu'aan to live. However, steam and fire are very dangerous within the caves, and they come at a risk of melting the ice walls and creating structural instability. Nearly all disasters within the caves have come from this. Is was a fear of the zu'aan, in fact, shortly following the Awakening Age, that kin'toni would discover this weak spot and instead of trying to breach their underground settlements, they would light fires near the entrances, wafting in the warm smoke and causing the walls and ceiling to tumble over, burying the zu'aan inside.
Previous to the Awakening Age, zu'aan simply used the surface and insulated rooms to practice forms of exaggerated heat. However, ever since the outbreak it has been very difficult to avoid causing the rock to falter, and the onset of the Shattering Age is a small gift to the zu'aan, as it solidies further the walls of this ice tomb. The lack of lighting is also a problem that the post-apocalyptic zu'aan have had to worry excessively about, as lighting sources from the modern ages have all but disappeared. Many have left Arynietu since then.
Plant life in Arynietu is extremely scarse, as one would expect. There are a number of ice adapted plants living in the region, though these are rare and can only be found near the surface. A great number of flora that's present in Arynietu was introduced artificially by zu'aan hundreds of years ago, to ensure the maintenance of the atmosphere and stable food sources. Many of these developed wild cultivars that escaped onto the wild, and some of these also lost public interest with the decades, becoming obsolute and ultimately part of the wild flora. Here are a few examples of plants that survive in the wilderness of Arynietu up to this day: Nonnahs, known regionally in some areas as nonnak, a pale green root that can surprinsingly survive in pure ice.
They have the ability of sucking up the nutrients in frozen water that develops consistently on the surface. Rainwater that trickles down the cavern roof absorbs the minerals on the rock, before reaching down and freezing on the floor's surface. This fresh water, packed with minerals, is perfect and ideal for sustaining plant life. Most plants, however, do not have the capacity or the ability to breach the ice to retrieve the nutrients, or to sustain their roots inside the ice without perishing. The nonnahs was bred for that single purpose. Plants of a certain genus were made to undergo a process of selective breeding in which only those plants with the strongest roots were allowed to reproduce.
These plants were then planted alongside the ice sheets in the zones that received the larger amounts of ground precipitation, and left alone to reproduce. They can nowadays be found in small grass patches alongside the larger basins of Arynietu, slowly spreading along the ice sheet. They do not live very long, and so their rate of reproduction is more or less in par with their mortality, making them appear as though they slither along the ice, which is also the origin of their second name, nonnak. In any case, they are a pale green type of grass with a medium root, about three inches wide and one across, made of a flaky yellow tissue. This organ helps the plant extract minerals from the ice water and provides the roots with a level of artificial warmth so that they may survive in the ice.
Their leaves do not receive sunlight, so they are mere acessories leftover from the days the plant lived on the surface. They are very thin and narrow, a very pale green, and are barely visible in the dark caverns, almost like hair follicles. Their root is edible and has a very mild and watery taste, similar to juicier fruits from the south. It is mostly made of ice water that it absorbs, in reality, and has little other components aside from plant tissue. Still, it is eaten by the locals as a sort of treat. It does not provide much of anything when it comes to nutritional value, so they simply enjoy it as something that feels good to eat. It is commonly eaten raw or used in cold desserts, or even as an accessory to grilled meat dishes.
The locals take care when harvesting them since they are aware that they reproduce very slowly, and they are not truly needed in their diet. Occasionally they are also planted, though this has proven to be difficult, as their seeds are hard to remove from the root.
Animal life in Arynietu is strange and sparse. Here are a few examples of local specimens: Cnei'wl, a large reptile with short, jointed legs adapted to easily slither around the jagged landscape of the caves. They come in a pastel variety of colors and have a thin layer of fur covering their entire bodies, which they use to keep warm during the cold nights. The fur is very thin and needle-like, and grows between their scales. It has adapted to interfere with the evaporation of their sweat, keeping moisture in, and brings them heat and warmth during the day and night, though they still prefer to remain in the small patches of sun scattered in the caverns.
They are quite large, up to 4 meters in lenght, though most of this measure is focused on their tail, which may reach up to 2.8 meters in lenght making it the bulk of their bodies. They have strong bones with many joints, that allows them to crawl around the cavern rooftops with easei, as well as determine strenght and intensity to a very precise degree. Rear and front legs are pretty much the same, with the rear legs having a bit more muscle tissue. At the end of the leg is a curved foot that allows them to grasp and hold onto the tough terrain without bruising themselves, as well as walk and run at high velocities without hurting themselves. They have very lenghty tails, as mentioned, and very narrow and thin bodies, so that their bodies are allowed to carry them efficiently.
As a downside to their incredibly mobility, they have almost no neck, as it would interfere with their movement, and their wide jaw and face is almost entirely within their body. They use their clawed feet to bring dig insects and other small critters out of the ice, and are strictly carnivores. They live in small packs and despite having natural predators, they can generally outrun them all. Usually, this would cause predator life in the caves to evolve means of hunting them more efficiently, or it would cause the cnei'wl population to spiral out of control, but animal life in the icy caves is already sparse, and zu'aan presence has made it even sparser, aside from plant life.
And even though they remain strong and existing today, the mere presence of the zu'aan keeps their numbers in order. One could say that their main predator is the zu'aan. Balej, a large insect with five eyes that inhabits small crecives and shallow caves in the underground Arynietu. Their bodies take the form of horizontal baloons, and have no limbs, making movement without the use of flight a near impossibility. It moves in air via small, frail wings, which come in pairs of eight spread across its body. It is blue in color and has the ability to inflate itself and turn orange sight of predators or danger, making its body seem deadly. It feeds on plants and bacteria in the ice and is largely unmoving.
They can almost never be found flying, despite their wing adaptations and lack of wings. They are toxic and cannot be eaten, nor touched, as they will cause long lasting skin irritation. They are not deadly, however.