Manadus is the fantastical world in which the "Shadow of the Silver Spire" campaign takes place.
Manadus is a vast world, and no mortal has traveled across it entirely. By studying the movements of the sun, moon, and stars, scholars have determined that Manadus is flat and circular. The Silver Spire is located at its geographical center. The Spire is in the tropics; as one moves further away from the Spire, one will encounter increasingly cold climates.
Most of Manadus is barren wasteland thanks to the destruction wrought by the Cosmic War. Pockets of civilization have cropped up only in those scattered places where the environment is not outright deadly to sentient life.
There are three major known continents. Orom in the south, Letalium in the north, and Aarakon in the west. Orom is the home of the Silver Spire itself. Only the northern half of Orom, dominated by the Kingdom of Aviok, has been well-charted by Men. South of that lies the vastness of the Great Desert. The Desert is so massive and inhospitable that almost no-one has ever managed to cross it.
Letalium is the most well-charted of the continents. The people who live there tend to think of it as two separate continents, which they simply call "The West" and "The East." Western Letalium is dominated by the young nations of Men. Easter Letalium is divided into two regions: Endara and Lung Kuo. Endara is the only place in Letalium where the Old Races of beast-folk still reign supreme, and is one of the last surviving forests in Manadus. Lung Kuo is a land ruled by the Scalelords, a loose confederation of powerful dragons.
Aarakon lies west across the treacherous Twilight Ocean. It is most uncharted, and little is known about it. Like Endara, Aarakon is home to a variety of beast-folk, most notably the Aaracockra, who are generally hostile to outsiders.
Manadus was created by the mother goddess Hetama'at. Some believe that Hetama'at is dead. Others say that She is merely resting or has departed from this plane of existence. In any case, She no longer rules Manadus directly. In Her place She left her two eldest sons: Rakhmet, the god of light; and Keth, the god of darkness.
Accounts of how exactly the Cosmic War began vary, but what is certain is that Rakhmet and Keth quickly turned against one another in their mother's absence. They fought an epic conflict against one another which lasted ten-thousand years. In the fallout from their war, most of the world was reduced a toxic wasteland.
Ultimately, the Brother Gods came to a truce. They would both depart from the mortal world; Rakhmet to Heaven and Keth to Hell. Each would rule their respective realms and could only influence the mortal world indirectly. As a sign of their pact, they constructed the Silver Spire to connect Heaven, Earth, and Hell.
In time, a band of human survivors settled at the base of the Silver Spire, and founded Aviok - the Silver City. Over the centuries, the nation of Aviok expanded into the mighty Silver Empire. At its height, the Empire extended across all of northern Orom, across the islands of the Twilight Ocean, and over nearly all of Letalium.
In the year 1080i of the Imperial Calendar, a massive beast called the Devourer appeared at the Empire's southern border. It was seemingly invincible, and rampaged across the Empire trampling entire cities and eating every living thing in its path. After a year of carnage, the Devourer was sated and returned underground to slumber. In its wake, the Silver Empire was no more.
Not long after this, T'ang Lung, Mother of All Dragons, fell from the sky to Eastern Letalium. She met little resistance as she and her horde of dragons and dragonkin spread across that part of the world, enslaving what native humans remained there. The lands conquered by T'ang Lung's spawn came to be known as Lung Kuo, or Dragonrealm.
Beyond Lung Kuo, the mortal races have begun to rebuild what was once lost. From the ruins of the Silver Empire, several smaller nations have sprung up to resurrect civilization.