Safir appear humanoid in their outward features; according to the theory of convergent evolution, their original native planet (which is unknown) must be similar to Terra. They are not genetically related to humans, though.

The ideal resting safir body temperature is 32 °C (89.6 °F). They are as such attuned to colder climates than humans.

The safir vocal apparatus is a syrinx, like that found in songbirds, rather than a larynx, as found in Terran mammals.

Safir skin is blue in color due to their blood being hemocyanin-based, rather than hemoglobin-based as in humans. From the head protrude two large, elven ears which, some human biologists theorize, function like antennae to detect extremely subtle behavioral cues from other safir, thus allowing safir in the vicinity of each other to communicate through what appears as humans to telepathy. Safir anatomy textbooks, however, while noting that the tips of the ears are rather sensitive, state that telepathy (or meraki, as it is known in Âirumâli), and other mental abilities emblematic of the species, proceed solely from the brain.

Formal research into the biological and metaphysical process underlying the safir's psionic abilities is slowly ongoing. Safir researchers do not yet know for certain how psionic powers — especially telepathy — work. From brain scans of safir and other species psionic and otherwise, they know that some structure exists in the brain that is responsible for psionic ability, and theorize, based on studies into the underlying mechanism of psychokinesis, that higher spatial dimensions may also be used in the process.

Some safir, mainly belonging to a royal line of carefully selective interbreeding over hundreds of generations, have retained birdlike wings, large enough for telekinetically assisted flight. The presence of such wings in safir royals has befuddled safir historians for millennia.

Safir reproduce in a manner similar to humans, and are viviparous; one notable difference, however, is the presence of ažaraw (sg. ažar), a gynomorphic third sex that are capable of siring children as well as bearing them, and gakeňaw (sg. gakeň), a fourth sex of sterile agender AMAB safir. The average heights for female, ažaras, and male/gakeňas safir, respectively, are 1.96 m (6’ 5”), 1.83 m (6’), and 1.57 m (5’ 2”).

Safir are known for their unbalanced sex distribution: of every 10'000 zygotes, there are 96 gakeňas, 964 male, 804 ažaras, 4'034 female, and 1'681 FF zygotes, as well as 2'420 that fail to implant, resulting in a sex distribution of 3:25:30:125. This stems from 49.2% of safir gametes having no sex chromosome, 41.0% F, and 9.8% M — as with their planetary origins, the cause of this chromosomal, and hence sex, imbalance is unknown.

Safir tend to live long. With adequate upbringing, nutrition and exercise, a normal safir life ranges from 560 to 625 Terran years (450–500 Daian years). In spite of this long lifespan, maturation occurs relatively quickly. Safir are fully sexually functioning at the age of 19–25 (Terran). They remain juvenile at this age, however, reaching full adulthood around the age of 60 (Terran).

From this point onwards, the biological mechanisms of the body are put into stasis. Unlike humans who start decaying as soon as peak adulthood is met, safir physiology remains constant for several centuries. Aging, thus, begins at the age of 500 (Terran), where, relative to their lifespan, an onset of rapid decay begins, lasting till the natural death.

Traditional safir society appears to be matriarchal. This is reflected in uterine safir being larger and more dominant than their spear counterparts. Additionally, the sex distribution of safir is heavily skewed towards female births. As such, historically, safir societies have tended to be polyandrous, though these days polyamory and/or monogamy appear more and more common.