The Cataclysm, colloquially known as "The Great Cataclysm of 2675" was a massive geological event that occurred on Aiers in 2675 a.a.H. It was responsible for causing a great deal of destruction across the planet and also for reshaping it as well. The event lasted 25 years and is typically associated with the end of the Fantasy Age and the start of the Modern Age.
During the climactic ending of the Third War of the Power, a 'holy' ancient human artifact was uncovered, that dated back to the forgotten or legendary event of the Apparition of Humanity. This artifact was a working device that dated back to at least the first century of the Apparition of Humanity, and was a device, used for 'terraforming' the planet of Aiers. Triggering the device would cause ongoing geological shifts and transformations in the continents of western Hieyoks, Aels, Zarhuy, and Ushaenor.
Aiers would terraformed so that its continents would roughly look like those of earth. Aels would be fused with Hieyoks and the two would look much like "Eurasia". Likewise, the northeastern section of Hieyoks would be split off and fused with northwestern Ushaenor. The New continent of Amparpica would emerge, rising from the Yiss Ocean floor centered at the southern pole as an 'Antarctica'.
Ushaenor would be almost divided in half, its low lying jungle and marshy rainforests would be largely submerged and drowned by the process initiated by the device. Huge areas of land of southeastern Ushaenor and southwestern Zarhuy would likewise be drowned as the land dipped beneath the waves. Ushaenor would come to resemble "North and South America", and Zarhuy would come to look more like "Africa".
Most of the continent of Hieyoks and the small continent of Zean, had already been transformed into extraterrestrial analogues of "East Asia" and "Australia" during the last fifty years of the first century and beginning of the second century following the Apparition of Humanity (50 - 120 a.a.H.). This was the reason for the world wide natural disasters and calamities that Aiers had mysteriously suffered during that period, known as the Age of Calamities, the chaos resulting from civilizations destroyed, or badly shaken, and veritable armies of refugees resulted in centuries called the Age of Invasions.
Why these devices used by the humans who had arrived and had begun colonies on Aiers had been programmed to make these specific changes or existed at all is unknown. These colonists from space, either from arrogance or desolation, felt the need to take such an extreme step to transform the planet into a quasi-replica of earth. One might speculate that perhaps earth was destroyed, instilling a need to tailor a substitute?
Vast regions and levels of the underworld of kazrrad were wiped out, mostly from collapse, or magma upwellings, or flooding from the seas. Certain lucky 'nodes' of the system, particularly those galleries and tunnels worked by the mysterious "World Builders" from the primordial past, were more likely to survive. Negeémiliel was a large, fortunate survivor, as most of the city was unscathed. Many other drow and dwarf settlements survived, but no known settlements of demons did, and the Draak Harg (dragon men) were hit hard, as were nearly all caverns inhabited by goblinoids.
Most of Kazrrad as an interconnected system of tunnels was destroyed as a usable system. The ecosystem collapsed, and even the lucky survivors found that there was no longer going to be sufficient food to maintain huge populations. Negeémiliel, for example, would be largely vacated for life on the surface as part of the rising nation states, many Negeémi would eventually become subjects of the Tork Empire of Cretor for example. As for Negeémiliel, much of the old city being abandoned, with outer alcove and tunnel gallery neighborhoods as ghost towns.
Polforia was a huge region in north central Aels, mostly known for being the mainland seat of the Dark Legion of Demons. It was also a specific target of the dreaded "human magic" that terraformed the Aiers planet to destroy the demons and end the Third War of the Power.
The geological result was the literal sinking of Polforia into the sea. Polforia was a low land surrounded by mountains, forming a geological bowl, this already made it a swampy area. Over the generation of severe ground quakes created by the human device, the land of Polforia sunk rapidly by almost a hundred meters, while the northern part of the Aels continent became distorted and 'unzipped' to open up to the sea. This process eventually allowed the sea to enter the deepening 'bowl' and drown the entire land.
During the time of the Cataclysm, the works of demons, Kanovs and man would be shaken apart by intense and endlessly recurrent ground quakes. The ruins and the land stolen by the demons, by the kanovs and humans before them, and the ancestral cradle of the elven race, would lie submerged beneath a new, shallow sea by the time the shaking stopped.