The second of the Precursor megastructures held by the Empire, Thalíär is a peculiar world by any standards. It is a three-layered shellworld – which is to say, it has three planetary crusts, separated not by simple caverns, but by skyvaults which can exceed a mile in height.

Unlike some shellworlds proposed by writers of speculative fiction, rather than being made up of continuous shells, Thalíar’s upper- and mid-crust are cut away in many regions to expose the lower crusts, and broken up by large shafts and canyons – the Clefts – permitting travel between the layers. Plant life spills freely down the walls of these canyons, and both natural caves and cut balconies offer spectacular views.

As the planetary gravity is relatively low, and given the multilevel nature of the world, flight is the most common method of transportation used on Thalíär. Wings are highly recommended as the most rewarding means of personal exploration.

THE ENIGMA OF THALÍÄR

The question everyone has when they come to Thalíär, even before they disembark from the Loadstone beanstalk, is how exactly it works. There should not, indeed, be any way that a three-layer shellworld could exist without reinforcements of exotic materials, and yet neither the walls and pillars which support the upper and middle crusts, nor the upper and middle crusts themselves, show any sign of such structural reinforcement. Rather, they appear in all ways to be native rock, showing no sign of the strain which ought to cause them to collapse under their own weight.

Those studying the shellworld at the Loadstone Geophysical Institute have recorded signs of extremely powerful magnetic fields interacting with bodies of superconducting orichalcium, various possible side-effects of metric engineering, and unexplained emissions of sterile neutrinos from opaque bodies buried deep within the planetary mantle.

All of which is no more than to say that they have had a great deal of success in defining the parameters of the enigma.

LOADSTONE

The capital of Thalíär, the jack city of Loadstone forms a circle around the base of the planetary beanstalk, sitting on the tip of a mid-crust promontory supported by a solid pillar beneath. The promontory itself is surrounded on three sides by a wrinkle in the Curtainfall. As such, the villas scattered around the perimeter of Loadstone enjoy spectacular views and perpetual rainbows as the waterfall cascades into the mid-crust’s Twilight Sea, and are some of the most expensive volumetric property in the system.

Other landmarks to be found in Loadstone include the Probable Technologies Academy of Crypto-Archaeology, the Loadstone Geophysical Institute, and the headquarters of the Megastructural Colloquium.

The CURTAINFALL and the STREAMING OCEAN

As well as the highest, Thalíär also hosts the longest waterfall in the Empire. The Curtainfall marks the point at which the uppermost crust ends in mid-ocean; prevented from draining in its entirety by a ridge of hard rock – as well as the replenishment it receives from the nearby Hydrocaust – the waters of the Streaming Ocean cascade down into the mid-crust along nearly a thousand miles of edge.

The EYE OF ALDÉRÉ

A single, ruler-straight shaft which descends from the highlands of the upper crust directly to the Undersea, the Eye of Aldéré is notable for providing an excellent view of the stars at any time of day. The astronomical orders of Aldéré have claimed the site as a hallows, and constructed a floating shrine to the eikone of the celestial vault thereupon.

GLITTERING HALLS

The Glittering Halls are a series of caverns large enough to house small cities, located within the planetary mid-crust. Massive quartz formations above the Halls, coupled with the cut-away upper crust above the region, allow natural light to penetrate miles deep and illuminate the caverns. Plentiful geothermal energy, meanwhile, bubbles up from the solid pillar below. It is one of the most populated regions of Thalíär, centered around the cities of Shimmer, Brilliance, Scintillation, and Tinct, and the buried industrial center of Drophammer.

SARDAL’S PEAK

The highest mountain on Thalíär, readily identifiable by its unusually flattened peak, Sardal’s Peak rises 28,947′ above upper crust datum. It is named after Sardal Elemtieros, the first-in scout who first set foot on the planet in 4196.

The SKY’S TEAR

A roughly teardrop-shaped section of the upper crust connected neither to the main body of that crust nor to the mid-crust below it, the Sky’s Tear is an island floating free in Thalíar’s sky.

Unlike the cloud coral islands of Torachal (Talie Marches), however, or the floatstone mountains of Calríäkay (First Expanses), the Sky’s Tear is a solid body of normal, native rock – just one, to the dismay of geologists, hanging in the sky in a manner not typically characterized by rocks.

The Sky’s Tear Exodochium, built into the island’s lower surface, is recommended to all visitors. The caves nearby house small populations of the airthia and xoxixa reconstructed by the Mythologae Immanentization Initiative, the latter in particular taking well to the intense geomagnetic environment of the region.

THUNDER WELL

As might be expected, Thalíär also plays host to the highest waterfall in the Empire. The Vorissevel river plunges over five miles straight down from the upper crust directly into the Undersea through the shaft of the Thunder Well. The force of the water crashing upon the volcanic plug at the base of the Well sends an endless peal of thunder reverberating for hundreds of miles across the Undersea.

The UNDERSEA, and the HYDROCAUST

Within the dusky world of the lower crust is the resting place of all Thalíar’s waters; a mostly-lightless ocean whose waters embrace much of the planet, warmed by geothermal vents, home to pale fish and darkness-adapted cephalopods, from minuscule plankton-feeders to the mighty kraken. This is the Undersea.

The most notable illumination found in this shadowy realm is the Hydrocaust. Where a series of deep clefts brings light to the ocean, a curiously stable magma plume also brings heat from below, raising the temperature in the vicinity to near-boiling. The plumes of steam gushing from these clefts are responsible for much of the cloud formation, and hence rainfall, on the shellworld.

The particularly heavy rainfall on the slopes of the nearby Precipice Range keeps the Streaming Ocean full, and so the Curtainfall spectacular.

THALÍÄR SURVIVAL COMPLEX

A city-bunker providing for the survival of civilization against the largest of natural disasters – potentially even such cosmic catastrophes as gamma-ray bursts or nearby supernovae – the Survival Complex is buried deep within the lowest of Thalíar’s multiple crusts. Armored in continental plates, this last redoubt rests secure beneath multiple protective layers of rock and water, miles-thick.

– excerpted from Leyness’s Worlds: Guide to the Core Worlds