Large, black- or white-and-violet spiders, two to five meters in length and four to ten meters in legspan, with two small eyes on its prosoma (head) and two more on its abdomen, above four to eight leg-like spinnerets three to seven meters in length.

The dreamweaver's physical senses are dulled almost to nonexistence, causing it to rely on its psychic abilities to make sense of and navigate the world around it.

Due to the near-uselessness of her four small eyes, a dreamweaver, like a blind safir, will often see via psychoecholocation, “pinging” the minds of nearby creatures to judge their size, shape, and position. A mesmerwright's vision, however, becomes, through unknown means, far more acute when spinning silk (q.v.), causing her to often use her copious thread to trap corporeal prey.

Dreamweavers smell and taste using two short, fleshy mouthparts called pigazei. Compared to safir, who can detect about 15,000 unique scents, mesmerwrights can only detect about 500. A dreamweaver's diet consists mainly of small insects and the waking minds of sapient beings, although, when needed, it can consume the silk in its body, or even other dreamweavers — this is very rare, though, as it takes almost as much energy for a mesmerwright to consume another as it will get from such an act.

The only part of a mesmerwright's body that is sensitive to physical touch is her spinnerets, which can be made so sensitive as to act as an organ of hearing (see ‘Hearing / Speech’, below). She often, therefore, uses these structures as fingers, putting them under and ahead of her in order to sense the terrain she is about to walk. Despite the psider's insensitivity to physical contact, she is particularly sensitive to kinesis, at least under laboratory conditions.

Dreamweavers are deaf in the conventional sense, possessing no bodily structures by which to hear sounds produced by you and I. Instead, they possess the ability to tighten the touch-sensitivity in their spinnerets to where they can sense the faintest of vibrations, or to psionically detect electromagnetic radiation from across the spectrum. These two mutually-exclusive methods of hearing form the basis of their two langauges: earth-speech, a simple, isolating language of clicks and snaps and stridulations; and dream-speech, an endlessly complex, highly polysynthetic tongue of electromagnetic pulses and waves, which, amazingly, most safir are somewhat capable of subconsciously decoding — although they cannot dream-speak as mesmerwrights can. Psiders must enter a certain kind of trance in order to use their dream-speech, and most of the species' higher classes will be permanently so entranced, as they see dream-speech as more beautiful and psyder-like than the lowly earth-speech.

A dreamweaver, like a blinded safir, will often use psychoecholocation, “pinging” the minds of nearby creatures to judge their size, shape, and position. Mesmerwrights are also capable of long-range telepathy, able to call out to sapient beings about 100 kilometres away — although these calls grow fainter and less coherent as distance to their recipient increases. Dreamweavers are also believed to project hallucinations onto those who touch them; this is usually the unconscious activation of a sapient's undermind by the psider's latent psi, but some cases have been shown to be psider-wrought hallucinations. Mesmerwrights possess the ability to teleport across vast distances and many planes — and perhaps even through time! — but careful study of dreamweavers has shown that this is a massive, sometimes fatal, drain on the creature's energy and thus rarely performed.

It is assumed that mesmerwrights reproduce like any other spider, but only because little is known about their reproductive processes. It is known, however, that psiders will often court one another by spinning long, taut strands of silk (see ‘Silk’, below) and using their rear legs and/or spinnerets to ‘pluck’ them as if they were the strings of a guitar (see ‘Hearing / Speech’, above); and that hellspiders are quite prodigious mothers, capable of laying thousands of eggs in one sitting, and hundreds, if not thousands, of egg sacs in their lifetime.

A mesmerwright's silk is one of the strongest fabrics, natural or artificial, known to mankind, able to resist ten minutes of direct exposure to a military flamethrower, as well as repeated assault by hunting knives and high-calibre rifles. Clothing made from dreamweaver silk is incredibly rare, though, as the process of dehallucinating the gossamer is little-known, very time-consuming, and can cause permanent damage to the safìr carrying it out. The method by which this silk is spun, though, is unique among arachnids: the dreamweaver will double over, somehow sharpening the vision in her four eyes, and use these eyes to ‘sight’ down her many spinnerets as they wave slowly about, silk extruding from within.

Very little is known about the societal structures of the secretive mesmerwright, although it has been gleaned from decryption of captive specimens' dream-speech that their society is highly stratified and authoritarian, with an Empress at the top, responsible for maintenance of the dreamweavers' group mind and most of its egg-laying, followed by several incredibly psionically powerful Overqueens who pull the Empress' astral threads; thousands of hermaphroditic, egg-factory Monarchs; and myriad other highly specialized castes. The total mesmerwright population in the Mesmer (q.v.) and its client colonies is estimated at 21 million.