Cannibalistic creatures once of the Prime, the psurlons are a vicious threat upon the Astral Plane that explore the breadth of psionic potential, thriving in their new home while searching for a Prime world to replace their long-since-destroyed homeworld.
Once a Prime species, the psurlons most likely have their origins in the distant past, thought to be one of the many aboleth experimentations due to their connections to the Far Realm. If true, this is a facet they carried over from their ancient creators, as the species once acted as one, directing their prodigious mental energies into charting the shores of psionic potential, seeking to use their abilities to improve and shape themselves in any number of manners. It was this exploration that led to their near-extinction, after an attempt to link their entire world in one great hive mind led to the rending of their original homeworld after the formation of a great astral rift. Most of their species was killed, but a slight few managed to survive the cataclysm, sucked through the rift and scattered across the Silver Void. Of the most powerful psions, including the ruling class, there were no survivors.
After settling upon the plane, they soon set themselves to finding a new homeworld, in the interim constructing citadels in which to dwell, great edifices in the same unnatural architecture that marked their shattered home. It of course wasn't long before they came into conflict with the githyanki, with the first recorded encounter and confrontation arising when both sought control over a psionic planar touchstone of great power. Seeing such a great people with such obvious psychic talent, the githyanki were the obvious target for the psurlons' enmity and jealousy. Their low numbers making them but a minor threat in the eyes of the githyanki, far busier with their wars against the illithid and githzerai at the time, the githyanki barely gave psurlons notice; a fact which enraged them even further.
Following this encounter and other similar fights, there was a great split in psurlon society, with some desiring to simply remain within the Astral and take it from these upstarts to prove the domination of psurlon talents. This split began to ripple through the handful of surviving psurlons, and aided along by the lack of their elder class to keep order amongst the many-varied psurlon minds, it was mere decades before the once-monolithic society itself shattered into dozens of clusters set against one another. While they were not so self-interested as to put the petty differences ahead of survival of their nearly extinct species, the tension within opposing clusters ground psurlon research nearly to a halt. In the thousands of years since, they have barely managed to hold on to their meager existence, some still searching for a world that could withstand the repetition of their past hubristic goals (Athas is a common target due to its pre-existing innate psionic potential), while others continue the "war" against the githyanki.
The psurlon people are divided into dozens of distinct clusters, each fervent in their belief that they know what is best for the still-weakened species and each seeking their own methods of restoring it to glory. Ever since the Mindstorm (as psurlons refer to the ancient cataclysm that destroyed their homeworld), the psurlons have been set against themselves philosophically, though only rarely has this ascended to physical confrontation. The psurlon people still hold enough respect for one another that they rarely let their differences of opinion rise to the point of outright warfare, finding even the idea of it offensive to the name of the "deity" they still worship today, the Far Realm entity Mak Thuum Ngatha.
Little is known about the nature of this entity, though many have noted its distinctly abolethian traits. Still, the worship of Mak Thuum Ngatha is just about all that still binds the psurlon people together. The psurlons were once ruled by an upper caste of beings of even greater intelligence than they, beings that are said to have rivaled an elder brain in power. They held the psurlons together as one great force, suppressing any difference of opinion promptly in order to let the species apply its formidable strength as one to problems of psionic research. Unfortunately, due to their great power, they were destroyed utterly in the Mindstorm, the immense energies of the Astral burning out their consciousnesses from within. With no upper class to guide them, and with the loss of nearly all psurlon lore (including the means of creating more of the upper caste), it was not hard for the strongly-opinionated psurlons to divide themselves so thoroughly. But even through this, Mak Thuum Ngatha still keeps them as one in spirit, its religion the one thing all psurlons can agree on. It is said to have formed the first psurlon, and to have recorded the rules by which all must live: survive, expand, enhance, and learn. The goals to which each cluster applies its own methods.
To outsiders, psurlons have an insatiable sense of superiority backed up (in their eyes) by their great minds and psionic abilities. Except in those instances where their superiority is proven false, psurlons view others as potential slaves at best, potential food at worst, but never equals. In situations where one can definitively set themselves above a psurlon, the shame and self-disgust cannot be matched; this is in large part the source of hatred they hold towards the githyanki, dating back to the first skirmish in which they were routed completely. There is unfortunately no middle ground when interacting with a psurlon, though their great skills in deception can lead many to think they are speaking on an even keel with one of this species; an illusion that has led many into an early death.
Though dwelling on the Astral today, psurlons are still mortal beings, still requiring sustenance as any other. Strongly carnivorous, they prefer the flesh of intelligent beings above all others. Humans and halflings seem to be their preferred prey, but any serves their hunger well enough. While they likely can survive on animal meat, most are utterly disgusted by the idea of eating something with no mind, seeing flesh and plants as food for "cattle", not befitting a proper psurlon. Even near-death, few psurlons will deign to feed on non-sentient beings.
Psurlons are a hermaphroditic species with no gender, self-fertilizing once in their life at a time of their choosing. It's unknown where psurlons raise these young, though most likely it's somewhere upon the Prime, just as the githyanki. A psurlon gives birth to between 9 and 14 young, believed to take about a century to reach full size.
After 900 years of age, a psurlon metamorphoses into their next state, known as the "elder psurlon". After a three-day-long binge, they enter a state of torpor for a month before finally awakening with their new shape. In this form, they have greater intelligence, greater power, and a noticeably larger form. These psurlons hold high positions in clusters, and the leader of a cluster is always an elder. Some rare psurlons change instead into a "giant psurlon" form, with no gain in intelligence but reaching nearly twice their original size. This mutation cannot be predicted until the stage is reached, but it reveals itself just before transformation; both the binge and the torpor last twice as long in these psurlons. Still, despite their great size and strength, they stand as mere equals to the basic psurlon in spite of this. It is believed that on their homeworld, there was some substance or ritual analogous to royal jelly that allowed the transformation into a third form, that of the now-extinct leader caste, but that knowledge has been lost to the psurlons since the destruction of their homeworld.
Psurlons live for an average of 1,500 years naturally, though of course on the Astral their lifespans are essentially endless; the long lifespans combined with the low growth rate have not helped any in restoring the psurlons to their former heights, nor have the casualties from their battles with the githyanki; present day estimates put the psurlon population at close to 4,000.
Somewhat oddly for a predatory species, psurlons have very poor vision; their sense of sight is limited to a dozen small non-compound eyes that can detect little more than contrast and motion. They more than make up for this in their other senses, though. The skin of their entire bodies serves to detect heat, vibration, and even sound, and they have extremely sensitive olfactory receptors lining the inner surface of their mouths, giving them a sense of smell that rivals nearly all species.
The basic, or "average", psurlon resembles a humanoid earthworm or centipede in ways, made up of a long, pink, tubular body about seven feet long, tipped with their small, black eyes and a fanged maw accompanied by a pair of mandibles. Psurlons have two spindly manipulator limbs ending in hand-like structures; though they don't have the full range of motion a standard humanoid possesses, they can grasp simple objects well enough. These "hands" end in thick claws, further impeding their ability to grasp but aiding in self defense. In lieu of legs, psurlons possess a dozen thin insectile appendages for forward motion. At full height, a psurlon is close to five feet, with the remaining length of their body bearing their walking appendages; the average psurlon weighs close to 130 pounds.
Elder psurlons appear to be bloated versions of the basic psurlon, their spinal surface lined with cartilaginous ridges. Their mandibles shrivel and fall off in the process of their metamorphosis, their skin darkening to a brick-red. In this stage, a psurlon has expanded by a full two or three feet, gaining a foot of stature and 75 pounds of weight. Giant psurlons expand even further, their skin fades to a dull, translucent grey and their spinal ridges appear even more prominent. Their bodies grow to 15 feet, their stature to 12, and they add a full 750 pounds to their bulk.
- Dark Sun MCII, pp.82-83
- Lords of Madness, pp.162-165
- Planescape MCIII, pp.76-77