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Ulshar (Planet)


Ulshar is the outermost of the seven planets that orbit the red dwarf star Qaphat. Ulshar has a mass about one third of that of Earth, and its surface gravity is a little more than half that on Earth. Ulshar is composed of a dense core and mantle with an unusually high quantity of radioactive and very heavy elements, surrounded by a thin, rocky crust and covered by a world ocean.

An overview of the Qaphat system. Note: Orbits are to scale. Planet sizes are not to scale. The orbital distance of Pyrdah to Qaphat is comparable to the orbital distance of the moon Callisto to Jupiter.


Ulshar's ocean varies widely in depth, as deep-sea vents that have remained active for hundreds of millions of years have slowly built up towering mountains of accreted rocky material. The average depth of the Ulsharri ocean is unclear, as is where the deepest part of this ocean is, or how deep it goes. Regardless, it is many times deeper than the oceans of Earth. Ulshar does not experience significant plate tectonics. Though the depths of this ocean are kept warm by the radioactivity and heat of the planet's mantle, the outermost few kilometers of this ocean are frozen as water ice. Beyond the ice is an extremely thin atmosphere of sublimated water vapor.


Although very little light from the ultra-cool Qaphat is able to pass through the icy crust of Ulshar, the planet's world ocean appears to glow of its own accord, as nearly all life forms in the oceans of Ulshar make use of bioluminescence. This includes the Ulsharri, the ancient and technologically advanced race native to Ulshar.

The Shallows

The outer layer of Ulshar is devoid of life, but nearest the surface of Ulshar, vast mats of pinkish single-celled organisms form, collecting the weak light that is able to pass through the thinnest parts of the icy outer layer. Other species form long, trailing strands that drift down from fungus-like filaments rooted into the ice. A few fishlike and mollusc-like species also exist here, some of which feed on the mats, as well as some larger predatory species.

Ulshar is a world with a high number of giant species, and many important megafauna on Ulshar come mostly from the mid-ocean depths, between 50 meters and 3000 meters. These large creatures come in a variety of shapes and exhibit a range of behaviors, from giant, undulating hunters to drifting, jelly-like filter feeders with bells nearly a kilometer a cross, to a host of sessile, coral-like species that grow on the sides of the vent towers. The Ulshar have found ways to make use of many of these species, some of which are kept as companions, some of which are used as beasts of burden, and some of the largest and longest-lived of which the Ulsharri have used as bases to build mobile settlements, sometimes inhabited by hundreds of Ulsharri, who are able to survive in a very wide range of environments, but who prefer the weak light, middling oxygenation, and higher pressures at this range of depths.

The Athrox, which grows to around ten meters in length, is often used as a mount by the Ulsharri.

The Depths

Further down the water column is a relative dead zone that spans from 4000 meters, where a thick layer of marine snow exists in equilibrium between the downward pull of gravity and the upflow of hot water, down to 15,000 meters, except along the ocean floor, where a biome exists almost completely independent from that of the shallower regions. Very few species range between the colder, shallower waters nearer the surface and the hot, high-pressure depths. The Ulsharri, along with other soft-bodied creatures, are able to make the transition between one region and the other, but the process must be undergone slowly, as the pressures in this region begin to reach levels that can cause individual cells to rupture.

The Ulsharri have not fully explored the furthest depths of their world's deepest points, but no matter how far down they have been, new and bizarre forms of life have always been waiting for them.


Qaphat has been hinted to be an alternate name for the star known on Earth as TRAPPIST-1, which lies in the constellation of Aquarius.


Leviathan's Children

ulshar.txt · Last modified: 2024/05/23 20:56 by pentabruce