The cosmology is the structure of the universe as it is known. It is an inexact science at best, as many cultures construct the cosmology differently, and even the wisest high priest or magus knows little of how it actually works.
The people of Northrim speak of a great world-tree called Yggdrasil, whose limbs and roots connect the Nine Worlds. Some believe the tree to be a metaphor for the magical currents that flow between the worlds, on which beings can travel. Others claim to have seen the great tree as a physical object, which is said to be visible far to the North when looking from the highest peaks of the Jagged Edge. Its limbs reach up to the High Realms, while its roots stretch down to the Nether Realms.
The High Realms
The Realm of Pure Light
An Elemental realm said to exist high above the highest branches of Yggdrasil, nurturing its leaves with light. Men of Achaea call it Aether and claim it is simply the atmosphere of Olympos, which the gods breathe. Those in the Cult of Astra say it is the untouchable abode of Astra Aeterna, far above the realms of all other gods. Men of Parsanshar call it Ahura and claim it to be the dwelling place of their own god. Magi doubt its existence, since they cannot tap into its power, though some lore speaks of magi who have done so. Regardless of its exact nature, it is universally regarded a mysterious and holy place filled with eternal brightness.
Aether, the Realm of Air
The Elemental realm from which air magic is drawn. Many men of Achaea equate it with the Realm of Pure Light, saying they are one and the same - simply the atmosphere of bright, pure air that the gods breathe. It is home to Djinn, Storm Giants, Sylphs, and more.
Home of the Olympian gods of Achaea. Said to reside atop the tallest mountain in the very center of the Jagged Edge, unreachable by mortals.
Vanaheim and Alfheim
Two interconnected realms that are home to the Vanir gods of Northrim and the ascended, immortal elves.
The Mortal Realms
The realm of men and most other mortal races. It is a flat plane of land and water, its central continent divided down the center by the enormous mountain range called the Jagged Edge. At the edges of Midgard, seawater eternally streams into the void. Somewhere deep in the ocean, this water is constantly replenished from the Realm of Water, Oceanus.
The so-called Dark Fields, a name for the subterranean world beneath Midgard. It is home to dwarves, dark elves (who call it Svartalfheim), goblins, and other, even less savory creatures. As large as the surface world but far deeper, it is home to a rich variety of landscapes and peoples, never touched by sunlight.
The land of the giants, located deep within the Jagged Edge. Some say it lies on a plane somewhere between the realms of gods and mortals. Others say that the only godlike giants are those that dwell in the elemental planes.
The Nether Realms
The realm of the dead is divided into several different kingdoms: Hades, land of the Achaean death-god; Hel, land of the Nordic death-goddess, etc. The landscape is as varied as the surface world, but far more terrifying, populated by nothing but warring demons and roaming spirits. It is also a realm of great wealth, full of precious metals that would be worth a fortune in the land of the living. While it is possible to reach the Underworld from Midgard, it is extremely dangerous and requires traveling deep, deep underground through Nidavellir. Precious few have made the journey and lived to tell the tale.
The Elemental realm of Ice, which is partially connected with Hel's section of the Underworld. Her fortress lies on the border between the two. The Realm of Ice is populated by Frost Giants and other monsters.
The Elemental realm of Fire, which is partially connected with the Underworld as well. A flaming, magma-filled wasteland of heat, home to Surt, a fire giant of godlike power destined to lead the army that destroys the world. Fire giants, ifrit, and salamandrae dwell there.
The Elemental Realm of Water, also called Oceanus, which is connected to the Mortal Realm and feeds its ocean constantly. It is composed entirely of water, and in its dark, underwater world dwell many terrifying sea monsters.
The Yawning Void
The great blackness at the bottom of all things, the Realm of Eternal Shadow. The Northmen call it Ginnungagap. The Achaeans call it Chaos. The men of Parsanshar say that Ahriman, the spirit of pure darkness and destruction, dwells there. Little is known of its true nature, except that pure shadow magic is drawn from there.