The Catastrophe was an event that took place during the Battle of Alent in the Second Great War and ended the Third Age. As warriors from the Magicracy of Alent, Crimson Coalition, Northern Horde and Southern Horde clashed, their magical attacks, along with an unholy ritual performed by the Totenkopfs in the catacombs beneath Alent and Archmage Jemuel drawing power to cast a spell to wipe out the armies threatening his magicracy, caused a volatile change in the already transforming Beacon of Alent which led to a magical explosion that changed the world and ushered in the Fourth Age.
Effects of the Catastrophe
What exactly transpired during the Catastrophe remains unknown to the world because those who survived it at ground zero lost their memories of the last days of Alent after having miraculously survived what took the lives of thousands of others.
What is known, however, is what else the Catastrophe caused other than mass amnesia:
The city of Alent was destroyed and left behind Crater Lake with an irradiated island that had a strange magical phenomenon known as the Anomaly in the surviving ruins of the once mighty City of Mages where a beam of magic still shoots into the sky.
The magical explosion caused a chain reaction that made both the Watcher in Darkness and the Essence in Light vanish along with their eldritch minions, the Starspawn and the Dwellers. It also caused the Blood Fever, a disease fatal to elves, to vanish overnight, and no elves have shown symptoms of it since.
The Godslayer awoke, destroyed Myridia in its wake, and flew off to the unknown. With the casualties to the Grey Cult's leadership in the destruction of their capital, the disappearances of High Prophet Xerathas d'Zarnagon and Captain Varalia Earthhaven, and the apparent abandonment by the Godslayer, the cult fell apart, leaving Aison in a state of uncertainty and upheaval.
The power of demons mysteriously diminished and made them fully mortal with a lifespan akin to elves, forcing them to adapt to their weakened state and learn to coexist with the other races. The surviving demon leaders signed what became known as the Treaty of Andaria to hold an indefinite ceasefire between the four rival hordes so they could adapt to their changed circumstances.
The powers of both the Clergy of Cardia and the Clergy of Mardük greatly diminished, signalling an end to both clergies as well as a crisis of faith to any of the faithful who had believed in their gods' return. Some clerics joined other clergies or vanished, while the Church of the Golden Dawn rose from the ashes of the Clergy of Mardük after coming to terms and joining forces with the Forgotten due to a revelation that removed the cloud from their minds although none can fully explain what caused this sudden change in them.
New, powerful and ferocious beasts of Shakkan appeared in the world since the release of the Hydra and began roaming the land, sea and skies. Their number included even many terrifying monsters from the Demon Realm. This effectively turned certain wildernesses in the world more dangerous to travel in than ever before as adventurers had to adapt to encounters with never before seen beasts with unknown, deadly abilities.
The undead known as the Wretched continued to expand their area of influence in Remon before the kingdom's landmass fell apart. Whether the undead survived the calamity or not is unknown, but what is known is that those still alive abandoned the land on ships, leaving it to desolation.
The continents clashed more violently than in the Cataclysm, causing some continents to join together while others split, some areas sank into the sea while entirely new landmasses rose from the depths in their stead.
In the brutal aftermath of it all, new kingdoms and autonomous city-states rose from the ashes of the fallen kingdoms. Libaterra became Andaria, Tevinth, Valencia and other small fiefdoms and city-states; the lands of Maar Sul and Scundia survived but in a diminished state, and the fates of Aison, Remon and Yamato remain unknown for now.
Thus began the Fourth Age.