Geography (Zyanya Supplement)
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Though occasional lunatics make claims about the world being a variety of shapes, it is generally accepted that the world is flat. The map represents the explored areas of the world. It is known that the world extends beyond the map, but the gnomish cartography guild notes that what little information has been brought back from those areas is insufficient to add to the map.
There is more to the world than this, this is just as far as the 'civilized' nations have established settlements. Beyond the continents depicted, there is a lot of ocean, and to date no ship has returned from voyages into the east, west, or south. To the north it becomes so cold that even magical protections become insufficient.