World Tree

The World Tree of Kaldheim is the binding element of the Ten Realms of that plane. It is located in the Cosmos. Esika is the god of the World Tree.

Description
The World Tree is the origin of all life on Kaldheim, and you can see the branches in the sky in all ten realms. However, they look different in each realm. The realms are constantly shifting and moving around the World Tree and can even collide. Such an epic event is called a "doomskar" and causes earthquakes, destabilization, and total chaos.

The light of Starnheim, shines atop the highest branches of the World Tree.

Tyrite
The skoti use a highly magical substance called Tyrite that is derived from the "sap" of the World Tree. Tyrite looks like the aurora-like lights of the Cosmos given solid form. While the gods may handle it safely, direct contact with Tyrite is quite dangerous for mortals. Esika makes a "Cosmos Elixir" from Tyrite, that slows the Skoti's aging and maintains their supernatural powers. Because of this elixir, the Skoti's skin or other aspects of their appearance show the influence of the aurora lights.

Trivia

 * The World Tree is inspired by Yggdrasil the World Tree of ancient Nordic mythology.
 * Tyrite's name is derived from the Norse God, Tyr.
 * Valla used to be a realm within the World Tree, before splitting off into its own plane.