Zudjari and Mosaic (Bureau)
In truth, their race is called the Zudjari. A militaristic species, they forego names and instead are referred to by rank and abilities, with a few exceptions. Their physical appearance is of a grey-skinned humanoid, slightly taller than an adult human male, with a triangular head, and a mouth, that while having a jaw structure similar to human, has "lips" that open horizontally, from chin to the top of their bald head. As XCOM investigates their biology and technology, their motivations and mechanisations become more and more clear.
Autopsy reports and notes indicate that they are more-or-less vaguely mammalian, as they are carbon-based, and have similar biological structure to humans, including eating, metabolism, etc. It seems that all combat forces are male (though the credits say that at least one class of Zujdari are voiced by women: the VA for Officer Chulski also voices Outsider Snipers), in that all Outsiders seen with bare chests have nipples, but male voices and dimorphism, and Origin himself is explicitly described in the alien's own texts as a male-- though while he is seen with full-frontal nudity, there is no visible genitalia.
Their skin is a pale, veiny grey, and seem to have a subcutaneous layer of non-Newtonian fluid: when subjected to physical force, their flesh automatically toughens in response, even when deceased. Their various body systems (circulatory, neural, muscle) have a variety of implants, including receivers to the Mosaic Network.
In their own language, the "Moz Zaaik" network. In our language, Carter is told "you would think of it as a broadcast," that can be transmitted through a variety of means, including infrasound frequencies.
Interestingly, one such frequency, 18.25 Hz, is close to the resonance of the human eye (18.98 Hz. If humans experience this frequency, pain and visual hallucinations can occur. This phenomenon is a hypothesis for "ghost" sightings ).
As said earlier, the Zujdari do not have names, and address one another through their classification: as Mosaic operates like a hive mind, individuality is literally near-nonexistant, so the Zujdari as a whole can nearly be described as a 'single' organism.
On top of the neural implants, there is a psychic component to the Mosaic network, so even if the implants are damaged or removed, some level of reception to the Mosaic network remains in once-connected entities.