Yggdrasil

Yggdrasil is the tree of life, that symbolizes the connection between the nine realms. The tree exists within cosmos and cannot be reached by foot alone. Within the tree, portals to the different nine realms are located where gods can travel between these different realms at will. The only way a mortal can travel between these realm, is in company of a god that can guide them.

How Yggdrasil survives

Yggdrasil thrives through a balance of being nurtured by three wells—the Well of Urd, Mimir's Well, and Hvergelmir—and by actively regenerating to counteract damage from creatures like the dragon Níðhöggr and stags that gnaw on its roots and leaves. The Norns tend to the Well of Urd, located in Asgard, and use its water and mud to keep the tree healthy, which counteracts the damage from other inhabitants.

Who lives here

Yggdrasil is inhabited by several creatures, including an eagle at the top, the serpent Níðhöggr gnawing at its roots, and the squirrel Ratatoskr which scurries up and down. Four stags (Dáinn, Dvalinn, Duneyrr, and Duraþrór) eat the leaves and buds, and a hawk named Veðrfölnir sits between the eagle's eyes.

The nine realms

The nine realms of the norse mythology are located on the branches and roots of Yggdrasil. These nine realms have different creatures and people living in them and different atmosphere and terrains.

Midgard: Midgard is a significant realm and the primary world of humans and mortals where there are almost no monsters. Instead, humans themselves attack each other for power and territory. The gods often visit this realm without revealing themselves to observe the humans and even sometimes joining the wars without using their powers for fun.

Asgard: Asgard is the fortified home of the Æsir gods. It is often described as a radiant, golden city in the sky, connected to Midgard by the rainbow bridge, Bifrost. Most norse gods exists within this realm. This is also where Valhalla is located, which is where the fallen warriors come to in their afterlife if they died an honorable death.

Svartalfheim: Svartalfheim is the realm of the dwarves, known for its intricate underground mines, vast caverns, and forges. It is a resource-rich, often volcanic or geothermally active world, where the dwarves live in settlements and produce the minerals and weapons sought by the other realms. The reason this world was called Svartalfheim, is because the gods didnt see the difference between the dwarves (dvergr) that reside here and Dark Elves that reside in Alfheim. Thus they called the realm Svartalfheim, instead of Dvergrheim.

Helheim: Helheim is the gloomy, cold realm of the dead in Norse mythology, ruled by the goddess Hel. It is the destination for those who do not die bravely in battle and is often portrayed as a continuation of life, where the dead live on in some capacity. While originally not depicted as a place of punishment, some accounts, influenced by Christian views, describe it as a more unpleasant or harsh realm.

Alfheim: Alfheim is the realm of the light and dark elves in Norse mythology, a world of beauty and light located in the highest branches of the world tree, Yggdrasil. It was a gift to the god Freyr and is associated with magic and inspiration. It is also the source of power for the Bifrost, and has been depicted with both bright and desert-like environments.

Jotunheim: Jotunheim is the realm of the giants (Jotne), a land of untamed, chaotic nature characterized by frost, mountains, and wild forests. It serves as the primary antagonist to the gods' realm of Asgard and is the source of much conflict, though some gods and giants intermarried. The river Ifingr separates it from Asgard and is notoriously difficult to cross.

Niflheim: Niflheim is a primordial realm of ice and mist, existing before creation. It is characterized by cold, fog, and poisonous rivers, and is home to the well Hvergelmir from which all rivers flow. Later, it became associated with the underworld and the realm of Hel, where those who died dishonorably went.

Muspelheim: Muspelheim is the fiery realm, home to fire giants and guarded by Surtr. It is the source of heat for the Nine Realms and plays a key role in creation and destruction, as Surtr is prophesied to help destroy Asgard during Ragnarök. The realm is characterized by volcanoes, ash, and rivers of molten rock.

Vanaheim: Vanaheim is the home of the Vanir gods, who are associated with fertility, nature, and wisdom. While its exact location is debated, it is generally described as a wild and chaotic realm, contrasting with the more orderly worlds of Asgard and Midgard. The name itself, "home of the Vanir," indicates its nature, and it is often depicted as a lush, wild, and magical place.