I want to talk a little more in depth about the greater cosmology of the nine worlds and the Underworld. This will take some time. First of all, some general information on overall structure.
1. Again, the nine worlds in the Chronicles are these.
a. World of Ice and Cold
b. World of Fire
c. World of the Light Elves
d. World of the Dark Elves and Goblins
e. World of the Dwarfs
f. World of the Gnomes
g. World of the Giants
H. The Heart of Heavens
I. World of the Humans
2. The ancient tree, Drasil, that came with the Shadowling, can be found in the Poisoned Forest near Myrkland. I am working on a map of the nine worlds as they relate to the Underworld and how they are all connected. The entrance to the Underworld that leads from the world of the Dwarfs is in the Poisoned Forest as well. (more on this later) map hounds will love this.
3. So in general, the main branches of Drasil are in the World of the Humans. However, the tree reaches all the way to the Heart of Heavens. The upper most branches rest there. The Heart of Heavens is the home of the One Outside the Seven and all the creators of all the worlds, including the seven (or now six :) that created Medelia.