Arth is a geographically huge. (Bigger than a ringworld kind of huge)
It is made up of semi-continuous biomes.
Each biome follows its own way, thus it has its own unique weather, ecology, social patterns, and rules for magic and tech. Most biomes are very, very similar to their neighboring biomes (hence the semi-continuous). Some are not. In some biomes they have different weather than the others, or a different moon, or a notably different ecology, or way for society. No matter what the way of the biome, each biome has a Pylon in it that seems to be the center of control for it.
GE-EM, the first god, is a collector. It collects/ copies things from other spheres and incorporates them upon its own world. It created a number of lesser dieties to aid in the "administration" of Arth. Thus a spiritual heirachy of five tiers was created. These dieties are everywhere on Arth.
Second Tier: GE-EM (post creating other dieties), Lady Arth (Mother Earth), Yi-Ang (Balance/ Chance)
Third Tier: Masters of Death, Time, and Luminance who become 4th tier light and dark.
Fourth Tier: Masters of the Five (Six) Elements: Fire, Earth, Air, Water, and Luminance/ Spirit- Light and Dark
Fifth Tier: Masters of XXX. These are the vast number of spirits in charge of everything else.
The Known World is the Elventi Imperium.
The Imperium is a Mid European Renaissance level tech world, with a well developed low level magic system. This is the "average" of all the biomes.
It is run by The Emperor (whos common name has come to mean Emperor over the centuries) and the Noble High Elventi. Each Land has its own High Elventi Governor. Administration below that is up to the local's choice. So your old king and his fedual lords, or your first senator, or your tribal chief, run the show for the Elventi. Those that rebel... usually don't last very long.
High Elves are immortal being of great power... imagine an immortal experienced Captain America/Batman, with access to IronMan/ Green Lantern power level item, and knowledge to rival a realm sorcerer (Dr. Strange/ Dr. Fate/ Tim) and has access to gate technology. There are not very many High Elves in comparison to the other races, but the standing imperial army only has 32 members and is enough to rule a surface area akin to the Earth's. Many of the Noble High Elventi have served in the Army for a century or four. Others follow more refined pursuits.
High Elves are full elves who have achieved the "next level". This process is a combination of physical, spiritual, and mental perfection, plus good genes and being in the right place at the right time.
The Elventi (Full Elves and High Elves) live on FirstLand. This area has 7 large biomes. Each biome is a Dukedom.
SecondLand has a number of biomes and one warp point (a place where stuff from other places "find" themselves. It is the current home of the 12 Humanti clans, the Amazonti, The Wapti (Landdwelling Squidish beings), and the Nikhon Orcenti (Our samurai are orcs). It is the home of 19 biomes (12 human, 2 amazonti, 4 of the great swamp/ wapti, and one of the island for the Nikhon.)
Thirdland is the second largest land in the Known World. It is filled with fractured biomes (a huge number of biomes of smaller than average size). The Imperium originally had mining colonies here (they shipped the humans here). Thirdland has the most biologic diversity as it has Elventi (including "wild" ones), Humanti (in a wide variety), Dwarfenti, Orcenti (Orcs of four types, Goblins, Hobgoblins, and Gremlins), Centaurs, Kerrenti (Wolf Folk), Putti (Cat Folk), and Gargoyles to name most of them. Note: things without the -enti designation are made species.
The main geographic features are the Three Human City States (Antioch, Amar, and Avon), The Kingdoms (Princedoms really... mostly agrarian feudal areas), The Wastes, The Great Plains, the Great Ridge (Huge Mountain Range home to Dwarves, Orcs, Goblins, and Skyfolk), and all those places inbetween. It is made up of hundred and eighty or so biomes.
Thirdland is the place where I tend to start a campaign group.
Northland is the largest land area. It is four times the area of Eurasia plus India. It is a preserve, untouched by the Imperium. In addition to being the home of the StarElventi, it contains giant mansized insects and godzilla sized monsters. A change from the two brutal meta races whos near constant conflict that makes travel there difficult if not deadly that I had originally placed here.
MaskLand is a 9 biome land that "appeared" a scant hundred years ago. The Masklanders (who are human) have a very unique culture based upon masques and costumes. They were brought here whole cloth from their world. They are the most "alien" of Imperial Peoples.
FourthLand: This is a 22 smaller biome land segregated between the coastal Lamic people (who are urbane, civilized, and religious zelots) and the more "primative" Engeti people of the interior (who see themselves of the caretakers of their world). It has only recently been brought into the Imperium, as both peoples have accepted Imperial rule (the Engeti accepting it first).
First Ocean is an 5 biome oceanic biome area where aquatic races live.
There is a "race" to find another Land to the far south of SecondLand (and East of Fourthland). Predictions show one is there. Some are exploring north of Northland, but so far nothing but terrible storms have been found.