Four Worlds (3.5e Campaign Setting)
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 Four Worlds: Coralia, Kharnala, Isten, Arcanala
The world was divided by the gods to ensure it's safety, now their people live separated by vast oceans and abnormal cliffs. Running through the middle of the world is a mile high vertical drop-off, leaving the northern half of the world on a higher plane than the southern half. The gods separated the lands to prevent a great catastrophe from taking place. The Empire of Coralia faces the approach of an ancient enemy, while the evil Yuan-Ti carry out a plot of world destruction from their homeland of Kharnala. Arcanala's nations war within them selves over mystical sources of energy, and Isten is preparing for a foreseen cataclysmic event.
Many years ago, when the kingdoms of the world were just beginning to rise up, a small band of wizards stumbled upon a book as old as the world itself. The band spent many years trying to decipher the books mystical codex, causing many to lose their minds. The band's leader, a young sorceress named Ancecna, stumbled upon the secret to decipher the book. The knowledge she learned corrupted her and the band with negative energy.
A celestial white dragon named Koron, representative of the gods, stumbled upon the corrupted band some time later. They called their leader by the name Vecna, which means "keeper of secrets." She had united the Orc tribes of the south, and planned to use them to gain power over the entire world. Vecna and her followers were crafting a suit of armor that would give them the power to raise and command their fallen foes in battle. Koron sent his follower, the gold dragon Rorc, to the gods with a message warning them of the band's growing power. The pantheon commanded Koron and Rorc to unite the people of the land and push the Orc army out of the southern lands. Koron gathered the people under the banner of the Coralian Empire and took his place (under a human guise) as their first emperor.
The Coralian army was gathered just in time to provide support to the Dwarven empire holding the borders. The Orcs were aided by the fallen soldiers on both sides, raised as undead abominations by the power of Vecna's armor. For every casualty the Empire suffered, Vecna gained a soldier. Determined to stop Vecna, Rorc sought help from the gods. The god of death, Nerull, forged a plan. He appeared to Vecna and suggested she craft a sword for her most prized general, the half-Orc Kas. When she presented Kas with his sword, Nerull spoke to Kas through the sword and tricked him into slaying his master. Though slain, a necromancer as powerful as Vecna has ways to avoid death. She used the knowledge from the book to achieve a death/god-like state. Today, scholars refer to this event as the only known historical example of what is called a lich god. Not fully a god, but something else beyond comprehension.
Kas was driven into madness by his betrayal, and took the what was left of his master (her left hand and eye) into battle. He lead the Orc army recklessly into the Empire's defenses, ultimately loosing the fight. The Orcs abandoned Kas and returned to their homes to avoid the race's destruction. Rorc trapped the mad general inside a tower near the Orc capital city, Skarr. He locked the tower and hid the key deep within the Red Desert.
The gods, upon seeing the amount of destruction Vecna almost caused, sent five titans to split the world into five continents: Coralia, home of the Coralian Empire; Kharnala, a land of psions and nobels; Arcanala, a land filled with overflowing magical energy; and Istan, who's inhabitants live in a hive-mind state.