Kulthea

Kulthea is the world in which much of the action of Rust of Coming Ages takes place.

Kulthea's most notable feature is a functionally impenetrable energy field that separates the eastern and western hemispheres.  The field extends under the ground to the limits of the atmosphere, somehow anchored to phenomena at the North and South Poles known as the Eyes of Utha. 

The "Western" hemisphere is the campaign world, for all intents and purposes.  The "Eastern" hemisphere is occasionally described as "madness," though it's not clear how anyone would know.

Kulthea's second most notable feature is the Pillar of the Gods, an upswell of planetary core material extending into the upper reaches of the atmosphere and surrounded by so many Essence Flows as to make it unapproachable.

Kulthea's third most notable feature are those Essence Flows, effectively an unpredictable - or unpredicted - weather pattern that carries the side effect of making magic possible.