The Nine Worlds

[Bricingwolf]

Cosmologist tend to break up the "worlds" or universes, into three groups of three.

The Spirit Worlds are worlds populated primarily by Cosmic beings. These are Yggdrasil, which is both the world tree and the universe in which it exists, Asgard and Vanaheim.

The Primeval Worlds are Muspel, a universe of "fire", Niflheim, a world of Ice and Ginnungagap, the Endless Void, which encircles Yggdrasil and is it's opposite.

Lastly are the Mortal Worlds, which are home to the mortal races. These are Midgard, home to Earth and Chevar, The Otherworld, the mysterious world of magic, and Jotunheim.

[Bricingwolf]

On Yggdrasil: The world of Yggdrasil appears to be an infinite land of forests, rivers and sometimes gargantuan lakes and inland seas. At it's center, as it is at the center of all things, is the World Tree itself. Incomprehensibly tall, and bigger around than most mortal towns, the World Tree is always visible, and somehow seems to always be about a days hard ride away, at the most, no matter how far you travel within it's world.
Upon closer inspection, an explorer of this world might stumble upon two surprising truths.
First, that all of the plant life of this world share the same root system, and thus all of them are part of the World Tree.
Second, this world is littered with "crossroads", or gateways between worlds. Not only to a seemingly endless number of points in the 9 worlds, but also to different points in time, and to worlds of myth and fiction, which should only exist in the imaginations of mortals.