Falx

Falx was a large planet with a high population of mind flayers and speculated by some scholars to be the original homeworld of the tarrasque species.

Description
From space, Falx appeared like a featureless white sphere. This was a result of constant, thick cloud cover, which masked the barren landscape below.

The planet was roughly 10,000 miles (16,000 kilometers) in radius, with a circumference about two-and-half times as large as Toril's at the equator.

The nearly perfectly round planet had a day length of 30 hours. Falx had no magnetic field, so compasses were useless there. Because of the thick cloud cover, it was never very bright during the day, and at night, it was utterly black. The dim daytime sky of Falx was green-blue, because the clouds absorbed more red light than a planet such as Toril.

Geography
Falx had a thicker crust than most other planets of its size with a smaller central core of nickel and iron. This led to less volcanic activity than other Earth worlds. There were no active volcanoes, hot springs, or other geothermal features.

The surface was relatively flat, with smoothed hills but no substantial mountains. The change in elevation from the highest point to the lowest point on the planet was only 8,000 feet (2,400 meters). The planet showed evidence of previous meteor strikes in its history, in the form of craters. These craters were postulated to have once been filled with water. The three largest such basins were called the Deadsea Basin, the Firestrike Basin, and Catastrophe Basin. Since all such "seas" were now dried up, the planet consisted of a single continent. In fact, there was no permanent liquid water anywhere on the planet, all water was found in the heavy cloud cover or deep beneath the surface.

Below the surface, there was evidence of ancient volcanic activity, in the form of massive networks of hollow lava tubes and subterranean lakes filling massive caves.

Climate
Like Toril, the axis was tilted, granting seasons to the planet; however, the effect of the seasons on climate and temperature was minimal.

The atmosphere had a high percentage of carbon dioxide, leading to a greenhouse effect that kept the planet very warm, about 150 °F (66 °C) on average. The temperatures were even hotter at the equator but cooler at the poles, although even at the poles, it was still so hot that water falling from the clouds as rain never reached the surface.

The high levels of carbon dioxide meant that it was harder to maintain a natural fire. It was also harder for most humanoid creatures to breath, and such beings grew tired quickly on Falx.

Lightning storms often flashed in the lower cloud levels, acting as strobe lights. The clouds began at an elevation of about 20,000 feet (6 kilometers)—where the temperature was about 80 °F (27 °C)—and extended upwards again about that distance. Winds were extremely strong on Falx, reaching hurricane speeds often.

Flora & Fauna
While sages speculated that Falx once had water and life on its surface, for all of recorded history, the planet was almost barren. The only notable surface flora were called "carpet mosses" because of their appearance and feel. These mosses formed colonies that could reach hundreds of feet in width and were mobile. Most were red or orange in color, but there were many distinct species.

All animal life was approximately reptilian. Most of these small animals were under a yard (meter) in length and had four legs, but some also had six or eight. Most were venomous scavengers who fed on both mosses and other lizards. There were many varieties, such as the Falx imbul. While the smaller animals and plants survived the heat and winds by hiding, the other major type of life form was simply large enough and powerful enough to resist such hazards. Falx was home to a population of several hundred creatures that were either tarrasques or creatures extremely similar to them. Some sages argued that the idea of the tarrasque being a unique creature was a falsehood and that the tarrasque of Toril was simply a specimen of the creatures from Falx that had been transported to Toril by some means unknown.

Inhabitants
All sentient lifeforms on Falx lived below the surface. By far, the most populous of these were illithids, although orcs and goblinoids also had a limited population. These latter two groups were used by the mind flayers as slaves and food. There was also a relatively large population of myconids.

Rumors existed of other sentient life below the surface, including marooned populations of dwarves and drow and even reports of aboleths in the deepest watery reaches of the planet.

Notable Locations
The two major illithid cities of Falx were called Brain-in-the-Skull and Tentacles-Grip-Tightly, when directly translated into Common. Each was ruled my a mind flayer wizard rumored to have been trained by an alliance with the supposed aboleths. The former city, with a population of over two million, was in the northern hemisphere; the latter in the south, with a population of just under one million. The elder brain of Brain-in-the-Skull was so developed that its telepathic range was over ten miles (sixteen kilometers)!

Both cities cooperated with each other, and in addition, there were numerous other outposts scattered about the caverns of the planet.

The illithids of Falx were not in any way ignorant of spelljamming technology, but for the most part, they kept to their own planet and considered how to dominate the other races living there. (A notable exception to this trend is discussed in the History section below.) The illithids defended their planet from any intruders, using such magics as astral projection and levitation to take out any ships approaching the surface.

History
In 1361 DR, illithids from Falx had heard about the Cloak of the First Pilot and were actively seeking it. They hired a mercenary named Barrab to apprehend the cloak from Teldin Moore upon his arrival on Toril, and their own vessels had even come as far as the orbit of Toril, where they happened upon the illithid historian Estriss, who had been lost in space after a battle with the neogi Prissith Nerro on board the Arcane vessel Nebulon. Estriss was taken aboard as a guest.

Some time later, the same illithids were still in Realmspace, near the planet Garden. Let by the illithid Netarza, they had captured an elven man-o-war and were attempting to learn more about the location of the dracon homeworld, when they had an encounter with Teldin Moore, which ended poorly for them.

Rumors & Legends
Some said that the aboleths were seeking a way off the planet and were working with the illithids to have their own spelljammers and spelljamming helms built for them.

Appearances

 * Into the Void (mentioned only)
 * The Radiant Dragon (mentioned only)
 * The Ultimate Helm (mentioned only)