Nivil is a planet in the Spelljammer campaign setting.[1]
Overview[]
From the edge of the system, Nivil looks like a fine blue ribbon forming a great circle around the sun. Closer in, the surface of the ring appears much like that of any standard earth world: blues, greens and browns, overlaid with white streaks of clouds.
Nivil is a "ring planet": a narrow, thin strip of rock and metal that forms a complete ring around its primary. Nivil is approximately 50,000 miles (80,467 kilometres) wide and about one mile (1.6 kilometres) thick. It encircles its sun at a distance of about 45 million miles (72 million kilometres), which means the ring is 283 million miles (455 million kilometres) long. When viewed from space, Nivil looks like a ring of slender blue ribbon looped around its sun. However, this apparent slenderness seems to blind most people to the fact that Nivil has almost 100,000 times the surface area of Toril. Unlike virtually all other worlds, Nivil has no gravity. Instead, the ring planet rotates rapidly around its primary (at about 700 miles per second [18,776 meters per second]), and the centrifugal force generated is equivalent to Toril-normal gravity.
Nivil is composed of metal intermixed with hard igneous rocks such as basalt and granite. The laws of physics would imply that the stresses on a band of rock and metal only one mile thick, spinning at 700 miles per second, would instantly tear the band into fragments and spray them outward from the sun. The fact that this hasn't happened implies that either the laws of physics don't apply to Nivil, or that powerful magic is somehow involved.
Nivil has a breathable atmosphere approximately 50 miles (80 kilometres) thick. This atmosphere is kept confined by a continuous shield wall of mountains 75 miles (120 kilometres) tall around both margins of the ring. The fact that Nivil has no gravity other than the "artificial gravity" created by centrifugal force has one interesting consequence: it's possible to fall off the ring world! Theoretically, a person could climb the shield wall mountains, and step off into space. Once clear of the ring, the unfortunate mountain climber would "fall" free into space, directly outward from the sun at 700 miles per second, or 42,000 miles per hour (67,592 kilometres per hour)!
Because the entire inner surface of the ring planet faces the sun, there is no day or night on Nivil: the habitable surface is always sunlit. Neither are there any seasons. Nivil is perfectly circular, and its center coincides with its primary, meaning that every section of Nivil is always exactly the same distance from the sun, and sunlight always strikes its surface perpendicularly. To someone on the surface, this means that the sun is always directly overhead, and that it is always high noon everywhere on Nivil. The inner surface of Nivil resembles the topography of any other standard world, and includes mountains, valleys, seas and lakes. The tallest mountains are about 45,000 feet (13,716 meters) high, while the deepest oceans are only about 500 feet (152 meters) deep.
The outer surface of Nivil (the one facing away from the sun) is almost perfectly smooth. It has no atmosphere, and is always dark. An unsecured object cannot remain on the outer surface, since the ring's rapid spin immediately hurls it into space. The only way anyone can explore the outer surface would be from a spelljamming vessel. The vessel would have to maintain the same speed as the ring itself, and would have to maintain a perfectly circular course. According to what is currently known about spelljamming, this would be impossible: while full spelljamming speed is certainly fast enough, there is no way that a vessel could remain at full speed close enough to the surface for observation. The mass of the ring is more than enough to cause any vessel to drop to tactical speed. Thus the outer surface is completely unexplored, and probably will remain so forever.
Nivil is not volcanically or tectonically active. The continents do not "drift," and there are no volcanoes or other signs of volcanic activity. Neither are there ever any earthquakes. Nobody knows how Nivil came to exist. There are some sages who claim it was created by an ancient race who vanished from the universe millions of years ago; perhaps this was the same race which engineered the "ribbon world" of Radole. Others believe the ring planet was created by the deities of its crystal sphere. It seems rather unlikely that anyone will ever learn the answer to this question.
The entire surface of Nivil is very hospitable to normal forms of life. At "sea level," the air temperature hovers around a balmy 75°F (24°C). This temperature decreases with increasing altitude, at a rate of about 3°F per thousand feet. Thus, the temperature on top of a 10,000 foot (3,048 meter) mountain would be about 45°F (7°C). On top of the tallest mountain, the air temperature would be about -600°F (-351°C). The highest peaks are capped with snow, although snow never falls at the lower elevations.
The winds on Nivil are similar in strength to those on a terrestrial world. The only significant difference is that circular storms like tornadoes and hurricanes can't occur on Nivil (since they depend on the Coriolis force, which is missing on a ring planet). The winds can reach hurricane strength, but they always travel in straight lines. Cloud cover on Nivil is similar to that on standard worlds. Some regions of the ring planet will have blue skies, while others may be under partial or complete cloud cover. Precipitation is relatively common, and the nature of the precipitation depends on the air temperature. (Thus, at "sea level," precipitation always means rain.)
There are many oceans on Nivil, some of them significantly larger than those that exist on a standard world. These oceans divide the land area into literally thousands of continents. As with the oceans, some of these continents are considerably greater in area than the entire surface of some worlds. There are ten oceans that have come to be called "global oceans." These are roughly circular, and are about 45,000 miles (72,420 kilometres) in diameter - almost the entire width of the ring planet. Each of these oceans has a cluster of continents near its center.
Note that navigation on Nivil is largely a matter of convention. Since there is no magnetic field, compass navigation is impossible. The sun doesn't move, and the stars are never visible, so standard forms of solar or celestial navigation are impossible. The most commonly used references are the terms "spinward," "anti-spinward," "port" and "starboard." "Spinward" is the direction along the length of the ribbon that corresponds to the ring planet's direction of rotation; "anti-spinward" is the opposite direction. When one faces spinward, "port" is to the left (across the ring planet), while "starboard" is to the right. It is very easy to get lost on Nivil.[1]
Inhabitants[]
Nivil is so enormous that it is capable of supporting a great many distinct and independent ecosystems across its vast surface area. The clusters of continents within the ten "global oceans" have the most distinct ecologies, simply because the distances between these continents and the neighbouring land masses are so great (often more than 20,000 miles [32,186 kilometres]), that they have been able to develop along their own lines with very little interference.
The ring planet is home to virtually every known species, flora and fauna, that can be found in any temperate region, including animals and plants, and most monstrous creatures. Nivil is also home to virtually every sentient race in known space except for those that are undead, extra planar or exclusively subterranean. Nivil is such a big place that incompatible species are generally able to find a "homeland" of their own: a place where they're at least partially removed from the races that most want to eat them. If an explorer had enough time, they could find just about any intelligent race living in a stable society somewhere on Nivil.
Perhaps the biggest question about Nivil (after the question of its origin, of course) is, "how did all the creatures get here?" The only places in the known universe, apart from Nivil itself, where Krynnish kender rub shoulders with Oerthish Greyhawk dragons are those where the species were transplanted via spelljamming vessels. This leads many sages to claim that Nivil was "populated" by a race that possessed spelljamming capabilities: perhaps the creators of Nivil and the engineers of Radole. Again, as with the origin question, there seems to be no way to get a definitive answer.
The intelligent races on Nivil have no insight to offer. The records of even the most long-lived creatures go back only 20,000 years or so, and none of these records describe any form of "spacegoing immigration" of new creatures. What this means is that, if Nivil was "settled," the settlement must have been completed over 20,000 years ago. The sentient races have their usual selection of creation stories describing their own origins, but these are no different from such myths anywhere else in the universe, so researchers give them very little credence.[1]
Spelljamming[]
Knowledge of and interest in spelljamming varies from race to race, and from region to region of Nivil. For example, there are many human civilizations on Nivil that have no conception of spelljamming, while there's one advanced human culture - the Alanti - who use a limited form of spelljamming to travel around the ring planet.
Landing a spelljamming vessel on Nivil would seem to be impossible. After all, the speed of any given point on the surface is about 700 miles per second (18,776 meters per second), much greater than the tactical speed of any ship. However, a quirk of nature makes it quite easy to land. The technique is as follows: at full spelljamming speed, the vessel approaches the inner surface of the ring, and positions itself directly over where its captain wants it to land. It then drops into the atmosphere of the ring planet. At the instant that it enters the atmosphere (at an altitude of 50 miles [80 kilometers] above the surface) the craft drops back to tactical speed. However, the vessel is now traveling at the same velocity as the ring planet itself, and is now motionless with relation to the surface and to the atmosphere. It can now maneuver normally within the atmosphere at standard atmospheric speeds.
Leaving Nivil is a similar process. As soon as the ship climbs above the atmosphere, it immediately accelerates to spelljamming velocity sufficient to match the rotational speed of the ring. In both directions, this shift happens without the helmsman being fully aware of what's happening. There is no risk involved in either maneuver. The only problem arises in the case of an unpowered object, such as a person or a wrecked ship, falling into the atmosphere of Nivil. With respect to a free-falling object, the atmosphere of Nivil is travelling at 700 miles per second, and the object will suffer terrible heat damage from air friction. Obviously, virtually any creature that falls freely into the atmosphere of Nivil will be killed instantly.[1]