Keld under Ar and under the running moons

Welcome to the World Xaîn

Geophysical overview

Xaîn is the second world of the green F2 star known as Ar, which it circles in an elliptical orbit with a period of about 2.3 Terran Standard Years. Although slightly smaller than Earth it is a dense, metal-rich world with an extraordinary biochemistry rich in metalloprotein complexes. It is, by our standards, a hot, dry world, whose tiny but intense sun blazes green-white in an extraordinary yellow sky (due mainly to the presence of dust and certain organometallic compounds in the atmosphere).

At present, approximately 56% of the surface of the planet is occupied by dry land, the rest by ocean. There are three major continents, of which the largest, Xaldash, accounts for the majority of the planet's land mass. Central Xaldash is largely desert, while the extreme north of the continent extends to the pole and is occupied by ice-sheet and tundra. The most fertile regions are the eastern and western coastal strips, and the southern plains known as the Nulaai. The second largest continent, Kashr, is largely covered in rain forest, although part of the centre is occupied by a chain of large lakes. Akíma Lian, the third continent, lies in the southern hemisphere and enjoys the most temperate climatic conditions; the northern area in particular is well-watered, fertile, and composed of forest and savannah. In the south-west of the continent the land rises steeply, forming eventually the spectacular mountain range known as the Mironi, or Mountains of the High Dawn. Between Kashr and Akíma Lian the ocean known as the Akhdalxand is scattered with extensive series of island chains (the Archipelgoes), including several islands, such as Kaimöven and the great atoll of Tsund, which are both large and populous.

Xaîn orbits its primary in a rather elliptical orbit which takes 2.4 Terran standard years (or 900 local days of about 23.5 standard hours) to complete (the sikildar, or Xaîni year). Because the axial tilt of the planet is negligible (1.2 degrees from the vertical) the planet owes its seasons more to the substantial variations in distance from Ar, and hence in insolation, produced by this eccentric orbit. The inhabitants of Xaîn distinguish 6 seasons:

• Afri - the early season, time of thaw
• Shalth - the long warming and blossoming of the year
• Arshei - the brief scorching high summer
• Xeist - the time of cooling and fading
• Vigdru - the wet, raw season
• Xja - the sharp, cold depths of the year

Biota

Life appears to have evolved on Xaîn approximately 5 billion years ago, at a period when the planet was rather wetter than today. Xaîn is rich in heavy metals and the biochemistry of the native life-forms has adapted to incorporate these: thus, for example, arsenic and mercury are essential elements of the diet for most higher life forms. The respiratory cycle of the Xaîni cell is also unusual, involving the oxidation and reduction of alcohol as a normal part of the cycle (Terran lifeforms can produce alcohol as a byproduct of anaerobic respiration, but it is not energy efficient and ultimately poisons the cell).

The greater energy input from an F-class star enables the formation of a number of high-energy compounds in the flora; thus supplied, the herbivores of Xaîn have tended, where other constraints are absent, to grow large. The largest of these, the gzin, stand about 8 metres at the shoulder, and resemble a six-legged cross between a warthog and an alligator. Interestingly, there appear to be two distinct lines of evolution among the fauna, one quadrupedal, and one hexapodal: thus gzinna, sliththa, and 'eshedreth are hexapods, whereas siwwa, iriath, shikundarra, and kormakedraxa are quadrupeds.

The People of Xaîn

The planet's dominant species refer to themselves as Neisenna, or simply Xaîni; they are large bipedal carnivores who have had a high civilisation for over 100 000 years. They are advanced in the physical, but not the biological sciences, and are gifted mathematicians (with an octal numerical system), superb linguists, and enthralling singers.

Xaîni are descended from a smallish, solitary, arboreal predator, not unlike a forest cat. Under the pressure of climatic change, these organisms appear to have gradually moved to a ground-dwelling savannah habitat, adopting a bipedal stance, and becoming larger. A modern Xaîni stands 2 to 2.5 metres tall, has good vision and superb hearing, although the senses of taste and smell are less well developed than in humans. There are four digits on each hand, two fingers, and an inner and outer thumb. Each digit has a retractile claw about 3 cm long; the price of this is slightly less sensitivity than a human fingertip. The mouth has three rows of black, shearing teeth, not unlike a shark's. Their reactions are very much faster than a human's, and their body tissues are stronger. On Earth, such a formidable predator would probably not have had cause to evolve sentience. However, against something like a gzin, even a Xaîni is relatively feeble. This combined with the gradual warming and drying of the planet seems to have pushed the species into the development of intelligence and eventually self-awareness. Their subsequent history has been long, sometimes savage, often tragic, and marked by the construction of an art and literature of great beauty. The story of their civilisation is the story of the triumph of will and intelligence over instinct, for unlike humans Xaîni are not, by nature, a social species.