Hârn is a fantasy setting, designed with the goal of verisimilitude, and it takes painstaking care to detail many many small areas that are frequently left out of the more broad brush strokes of other game settings. Something like thirty man-years of effort have gone into creating the setting from N. Robin Crossby and his fellow players.
It contains star charts, vegetation maps and notes, prevailing winds and currents, tectonics and vulcanism, in addition to all the common features such as cultural information, and more common geographical features.
The following pages will hopefully serve as a link to the HârnWorld setting and specifics of information about the world that Hârn exists in, as opposed to the more general information available elsewhere and in the above links. These pages are collections from the Encyclopedia Hârnica and other various HârnWorld products.
Kethira is Hârn's planet. It is the second of five planets of the star Nolomar. The planet is slightly smaller than Terra and has one moon called Yael. It is predominantly a water planet. Oceans and seas cover seventy eight percent of the surface area, including two large polar ice packs, neither of which cap any continental mass. There are only three continents, in order of size: Lythia, Mernat, and Kamerand.
 Kethira: Sky & Stars
Few Lythians have any real knowledge of astronomy. Most of what there is rests with pilots, astrologers, and mages, those whose livelihood depends on their familiarity with the stars and constellations of Kethira's sky. But even casual skywatchers cannot fail to note that the night sky changes with the seasons in an endlessly recurring pattern. Only the planets seem to wander aimlessly about the heavens but even the mystery of their courses will yield to diligent study.
Most star gazers study the heavens intent on discovering patterns that can be related to the lives of men and kingdoms, knowledge whetted by a desire for the power gained through successful prediction of the future. However, a few arcane loreists practice true astronomy. They own a few telescopes of widely differing capabilities, each a jealously guarded secret.
 Kethira: Natural Vegetation
Kethira, being a fully temperate world of approximately 1AU from its primary has the full range of vegetation that any earthlike world would. The vegetation map details the rough outline of typical vegetation types, and where they are found.
 Kethira: Prevailing Winds
Winds are driven by the same forces as ocean currents, but air is far more fluid and volatile than water. The effects of wind are even more important than ocean currents to mariners and to the climate. It is the wind which allows heat exchange between the surfaces of ocean and land. Prevailing winds carry moisture inland, feeding rivers and vegetation. However, by the time winds reach deep into continental interiors, or cross mountain ranges, they have lost all or part of their moisture content and speed. As a consequence the continental interiors are arid and subject to temperature extremes.
The movement of air masses is extremely complex, especially where the topography interferes. Winds and currents work as a team, their effects are greatest where they are close together. Hence, prevailing winds are less meaningful inland than in coastal areas.
 Kethira: Major Ocean Currents
The configuration of oceanic currents is determined by the Coriolis force of the planet, the shapes of the land masses, and the tidal effects of any moons. In general, currents moving away from the equator are warm; those moving away from the poles are cold. Where hot and cold currents meet, fogs and mists are common. The map shows only surface currents. It may be assumed that there are additional deep currents. Ocean currents have two main effects on the inhabitants of Kethira. Mariners who wish to make good time can greatly benefit from knowledge of them. They average one to three km/h and this can make a great difference in travel time on a long voyage. Ocean currents also have a profound effect on climate. A warm current moderates the weather all year round. Northwestern Lythia would be far less pleasant, and much colder, were it not for the North Haonic Current that runs from Kamerand to Harn. The ocean distributes and equalizes heat over the planetary surface, cooling the land in the tropics, warming it in high latitudes.
 Kethira: Tectonics & Vulcanism
Kethira has a nickel-iron core kept solid by immense pressure. Around this is an outer core of the same composition, but liquid. The bulk of the planet is a mantle of various compressed iron-magnesium silicates which are fairly rigid to a depth of about 720 kilometers. The outermost layer of the mantle is a crust, rocks formed from gradual cooling, which has fractured into a number of large plates.
The fact that the surface plates are floating on a semi-liquid mantel does not result in a particularly stable situation. The plates drift slowly across the surface. Where they rub against each other the friction causes earthquakes. Where they are moving apart, the molten rocks of the interior exude in volcanic eruptions. Where an oceanic plate slides under a continental plate, the upheaval creates a mountain range along the discontinuity, and a deep oceanic trench offshore.
The picture is more complicated than this however. The plates are not of uniform thickness or consistency. Isolated hotspots exist where the plates are thin or perforated, resulting in solated volcanic activity and local hot springs. Some plates are "softer" than others. The Azeryan-Karenjia plate, for example, is in the process of being broken apart by the larger and firmer plates to the east and west. Complex warping dictates that this part of the planet has more than its share of natural disasters. The eastern part of the East Lythia plate is also soft and will eventually be crushed. All such effects exist in varying degrees on Kethira.
All these motions are, of course, very slow. The residents of Azeryan and Karejiacan hardly notice the drift of continents. All they can perceive is that from time to time, the local conical mountain erupts, or the earth beneath them quakes, causing great hardship.