Doppelgangers (also known colloquially as "dopplers"), though often a scourge on Prime worlds, have little presence on the planes; most have scant interest in planar travel, and those of a darker bent find ruling figures on the plane poor targets for their infiltration, often holding as they do inborn talents that allow them to pierce their abilities or schemes. However, some few do find their way beyond the Material, largely congregating in urban environments much as they do in mortal environments, joining alongside or guiding changelings, or exploring the chaotic planes to better connect with their inner nature. On occasion, one can even find the occasional Cult of the Faceless Ones honoring their names, though only a handful of such have been found amongst the historical records of the planes.
Doppelgangers have little sense of personal identity, being so often forced to draw who and what they are from those around them. Their innate telepathy is constant and unending, pushing upon their minds a flow of not just memories, but personality and identity. While this is a necessary aid to their mimicry, it also tends to displace all that is themselves as an individual without intense focus or outside aid. It is only among their own kind (or others with an immunity to their mental abilities) that a doppelganger can truly be themselves, and can even identify what it means to be themselves.
It is due to this constant subversion of internal identity that the well-known hatred, xenophobia, paranoia towards other peoples, and desire for control comes to so many, for doppelgangers know that what they are is under constant attack from what others are both literally and figuratively, and for such doppelgangers it is only by pushing back against it and taking hold of the reins of society, directing it to their own whims, that they can feel any sense of control over themselves. This is often taken as a desire for power for its own sake, or a desire for pure material gain for its own sake, but in fact the core of the doppelganger is directed wholly towards seeking a mastery over their own identity that other humanoid beings take for granted. It is unfortunately uncommon amongst doppelgangers to be able to fight this natural inclination while among the societies of others, and so few even try. Among those that do, strict personal control and a fundamental imposition of order on their environment is necessary to maintain their sanity to a degree that may seem obsessive to others. Many sages have noted the interesting contrast of their fundamentally transmutative forms contrasting with their necessarily regimented personalities, and have sought insight into the fundamental contrasts between Law and Chaos through study of these beings.
Amongst doppelganger cities, rare as they are, they find their existence much easier. in such surroundings, they find themselves better able to explore the limits of their form, experimenting with a wide variety of physicalities much in the same way other humanoids would treat clothing, complete with patterns of fashion rising and falling over time. In such settlements, identity is no concern externally either, for doppelgangers can somehow always recognize and identify one another regardless of physical form; some theorize that it is their natural mental abilities granting them the ability to recognize some facet of one another's auras or mental patterns, while others believe it falls to their innate recognition of body language that they have honed out of pure necessity. Whatever the reason, whether purely among their own kind or having a chance encounter in the open world, doppelgangers feel a special kinship for one another as anchors in an unsteady world, considering all others of their kind as family regardless of distance or separation.
Cult of the Faceless Ones
Little is known of the Cult of the Faceless Ones, as few have left it and even fewer have managed to infiltrate it. What is known ties them to the mysterious creator figures of whom the doppelgangers occasionally speak, those ancient nameless wizards or godlings that first formed their species from human subjects in the distant past as servants and assassins in some form of shadow war. It is believed that this cult was first founded out of a desire to continue what they saw as the goals of said creators, pushing their natural inclination towards infiltration of the heights of power even further through subverting other mortals to the cause, simultaneously dissolving their sense of identity much as they themselves. They even seem to have some knowledge of the original rituals used to transmute the doppelgangers themselves, their mortal servants often ending up in a horrid midpoint between their original nature and that of the doppelganger, leading some to wonder if perhaps those original ancient creators may somehow still be involved.
Biologically, doppelgangers still have much in common with their human ancestors, even if they hold no similarity whatsoever to the casual glance. Their internal structure is still nearly identical, as are their biological needs; they still require food and drink as with a human, and their capabilities beyond their unique skills are about on par with any human. Of course, it is these unique abilities that they're most marked for: their shapeshifting and telepathy.
A doppelganger's shifting, though originally forged by alchemy and so carrying a spark of the magical, is a facet of their bodies rather than innate spellwork. It allows them to take the appearance and voice of any humanoid being reasonably close to their own height, regardless of bulk, and their mastery of body language allows them to mimic subtle details of movement, together granting them an excellent grasp at the physical aspects of their mimicry. The mental aspects come from their innate telepathy, which allows them to connect on a psionic level to most any intelligent mortal being. This allows them to not only gain details about their quarry (if posing as a specific individual), but also to note what is expected of them from those they're attempting to fool and alter their behavior appropriately.
In their natural state, doppelgangers are pale grey-skinned, genderless humanoids with painfully slim forms, arms and legs slightly too long for their bodies, and fingers and toes that almost seem stretched. Their height covers the same range as humans, but their weight is usually half as much as it ought to be, as doppelgangers hold not a single ounce of fat on their forms. Their bodies are entirely hairless, with bulbous heads and large, pure-colored eyes with slim, slitted pupils, most often white, yellow, or pale green.
- Dragon #80 - Psychology of the Doppleganger, pp.6-8
- Dragon #300 - The Minions of Darkness, pp.58-59
- Monstrous Manual (2e), pg.60