This is where the entirety of Season 1 takes place.

Your world is only 2,000 years old, but it is already dying. At least, that’s the conventional wisdom. Still, life goes on.
The gods created your world, and presumably still watch from afar—their priests can still channel divine power, even if the gods themselves are silent and un-knowable. Towering, colossal glass walls wrap around your flat earth, stretching up into the sky and narrowing, until they reach the sun. The sun, of course, is a ring of light that rests on top of the walls, and shines for part of every day, and then fades to a dim glow at night. It is only when the sun is dim that one can see the protective glass that sits atopthe world, the final barrier against what must be a dangerous universe outside. Only the four rivers falling from the sky enter from outside the glass.
No one knows how much longer the world has left before everything is baked dead and dry. Some argue that this is merely a temporary deviation. Indeed, some parts of the world have seen growing prosperity from the warming. Still, ever since the Godsriver ceased its steady flow and began to spurt through the glass, and then began to grow increasingly polluted with soil and algae, most people have become increas-ingly concerned. When the rate of flow of the Godsriver slowed dramatically 50 years ago, prophets and cults of doom became popular. Perhaps the end really is near.
Still, life goes on. What’s the alternative?
The world is flat and circular. Four large rivers pass through the glass from the four intercardinal directions. The River Reliable lies to the northwest, the Ardanianelle River to the northeast, the Hilt River to the southeast, and the Broken River (formerly the Gods River) to the southwest. These roughly divide the country into its basic political units, the Four Nations (discussed in the political section below). The rivers fall from the sky and run to the Middle Sea. No one knows where the water comes from, nor where it goes, but it has been coming and going since the world began. All the water is fresh (there is no salt water), and there are no tides. Small waves move toward Arrival, pushed by the wind and river flow.
Interesting geological features abound. Each of the four quarters of the world has several large mountains, shaped like giant rocks resting upon the land. The mountains are each made from a different substance: Iron, tin, cop-per, and stone make up the largest mountains, but smaller mountains of gold, silver, platinum, and mithril exist as well. There are said to have been boulders of adamantine at some point in the past, but they have either been stored some-where, or were used long ago. All of these mountains are occupied and mined by the various sentient races, and have gradually decreased in mass.
In the past people would break off pieces of the glass walls of the world, and use the material to craft precious goods and works of art, but damaging the walls is now considered taboo in most parts of the world. Magical glassteel weapons can still be found in the hands of some warriors or the wealthy, though they are not considered to be as effec-tive as mithril or adamantine.
The world has the standard four seasons, and they are regulated by the length of time during which the sun stays lit. A complete day/night cycle is 24 hours. During the summer the sun stays lit for around 15 hours each day, and that falls to around 8 hours in the winter. There are 360 days in a year, and the year is divided into twelve months, each with 30 days. The months are named simply First Month, Second Month, etc. Each month is divided into six weeks, each with 5 days: Oneday, Twoday, Threeday, Fourday, and Restday.
Weather patterns are mostly predictable. The heat from the sun warms the center of the world more than the edges, and the rising warm air causes cool air to be pulled in from the edge of the world. This means that the wind usu-ally blows from the edge of the world, toward the middle. This wind carries moisture from the rivers, and it often re-sults in clouds and rainfall. Rainfall tends to fall briefly in a mist or a steady, light drizzle, so creeks and streams rarely form. Rain is more likely to occur at night. Random variations in water flow and clouds prevent weather from being totally predictable, but long droughts or periods of prolonged rain are unusual. Or rather, that was true until the Gods River broke. The areas around it have become drier as a result, and the wind carries less moisture toward the center of he world. Other than this variation, the only other variation in climate is from the edge to the middle: The edges tend to be cooler, due to the reduced sunlight, while the middle tends to be warmer. Over the past hundred years, a clear warm-ing trend has taken place. The effect has been gradual, and some still wonder if it is temporary. The warming trend has caused agricultural production to shift closer to the walls of the world, and away from the center. The warming trend has been blamed on many things—insufficient faith in the gods, excess heat produced by arcane spellcasters, innovative machinery that burns fuel to produce power—but no one knows for sure. The breaking of the Godsriver may be contrib-uting to the warming, but academics cannot agree on how to test that theory. If this warming does continue, the conse-quences will be dire. Hopefully that fate is far in the future.
The soil of the world is dark and fertile almost everywhere, but the material under this varies from place to place. For example, the island of Arrival sits atop granite that rises from the sea. If one were to leave the island and sailto the shore in any direction, one would find that sand lies along the beaches of the sea, but under that sand lies a thick layer of water-resistant clay. Further inland there is even more variation, with some areas having sand under the soil, and others having large, round boulders. The earliest explorers who reached the edge of the world found that giant cu-bes of silica—like grains of sand, but larger than a house--lay buried under the dirt there.
Most people believe this world was created by the gods to be suitable for its residents. The gods may be silent and unknowable, but they must love the people of the world to have provided for them so thoroughly. On the other hand, the gradual warming, and the condition of the Broken River, have caused some to wonder if the gods have aban-doned the world.
The sentient races all awoke on the island of Arrival, in the middle of the world, 2,000 years ago. It is said that they all awoke at the same time, laying in a pile on the giant tarp that covers the center of town. It’s not the same tarp you can see today, of course; it has been mended many times, and is now more like a patchwork of smaller tarps.
Records from that time are not thorough or plentiful, but some do exist. The first peoples were all gifted with speech, and many knew written languages, trade skills, spellcasting, and other gifts, presumably from the gods, though none could remember anything else. They gave themselves names, and created a society, which spread from Arrival to the rest of the World.
As they spread, they found nothing but wilderness—no other sentient creatures existed, aside from the first peoples and their offspring. They did find five signs of divine favor, however, as well as the Soul Jar (discussed in a sep-arate section below). First, there is the patchwork of tarps that covers much of the island of Arrival. It is suspended 30 feet above the ground by stone pillars, which have crude rungs carved into their sides. The other four signs are giant stone numbers, one through four, set upon the ground, in the middle of what have become the four nations. Each num-ber is around four miles long, two miles wide, and 100 feet high. Cities have grown up around them, and eventually, inside them.
The four rivers quickly created natural barriers that divided the world into four mostly-stable nations. They have each changed over time—the Free Cities once spread over a larger area, partly into what is now the Magistracy, and the Iron Empire was once much less centralized—but there are usually four of them, in the same places as the na-tions are today.
The residents of the four nations and Arrival all speak Common, a language which evolved from the mingling of languages at the beginning of the world. Some groups of elves, dwarves, or orcs have isolated themselves to preserve what they see as their true culture, and continue to speak languages descended from their original native tongues. Most people have chosen to be more practical, and today, almost everyone you meet speaks only Common.
This is not a complete summary of all the important events in the world, or even the ones your characters know about. For example, your characters may know something about Observers, beings that were once thought to have a closer-than-normal connection with the gods, and were admired or even worshipped. Over time people became skepti-cal of them, and then came to fear them, until they were hunted down. Your characters may know more details about this if they can pass a history check, or they can learn more by asking others. The same goes for other subjects, such as the history of the Gods-eye (a giant lens high up in the wall of glass, also known as the Oculus), or the shadows that once moved behind the wall, or the stories of people who tried to reach the sun, or tried to burrow into the ground, and so on.
Source: The Player Guide
World 83
The Glass Guarded World is also known as World 83; it's one of a series of large glass containers where the wizards of the Research Complex placed shrunken-down residents of their world. The walls of the glass containers prevent divine magic from entering, sealing the worlds off from the deities of the world at large.