The Mortis are an alien species encountered by the Directorate approximately 100 years ago. They represent the greatest single threat to human existence in our species' relatively brief history, and are responsible for more human deaths than every war ever fought by mankind up to the point of our first hostile contact with the species. The Mortis are, compared to our own civilization, much more old and advanced. Although the Directorate is not aware of the fact, the Mortis hail from the Dwarf Galaxy of Canis Major, a satellite galaxy of the Milky Way (and the closest Galaxy to our own). No human being, to anyone's knowledge, has ever encountered an actual member of the Mortis species, and their existence is only a theory among Directorate scientists. This is because the Mortis wage war with a vast, essentially inexhaustable army of biological constructs - genetically engineered super-predators ranging in size from creatures smaller than a human adult to vast biomechanical space-faring monsters capable of taking on Directorate Navy capital ships.
The Mortis hail from an unknown star in the Canis Major Dwarf Galaxy and are theorized to have evolved on an earth-like world, judging by their marked preference for conquering Directorate-held Terran planets. Beyond speculation, nothing is known of their biology, history or motivations. It is extrapolated that they breathe oxygen and have a biology at least somewhat similar to that of Terran species, assuming the biology of Mortis Constructs reflects the nature of their creators.
Mortis is the name given by the Directorate to the vast array of biologically engineered creatures, originially thought to be a natural alien species unto themselves, presently assaulting the Milky Way Galaxy. What their alien creators call themselves - indeed, virtually anything about them - remains completely unknown. There is a distinct caste system and hierarchy among Mortis Constructs, and killing the "leader" organisms has a marked affect on their combat performance. The creatures seem to function in a manner similar to networked A.I.s, locked in a perpetual state of ethereal communication - generally taken to be telepathy - with each other. The strength and effect of this psychic signal grows with the number of creatures and their proximity to one another. It is unknown what the maximum effective distance of this network is, if any exists at all. Some scientists theorize that every Construct is linked to every other telepathically, but the majority theory holds that they form localized psychic networks that increase in range and power exponentially according to the number, nature and proximity of participating Constructs.
Whatever the case, this telepathic network is immensely pervasive and powerful. A reasonably intense system easily outstrips the utility of any non-FTL communication system in use by the Directorate. This is offset by the relative stupidity of most Constructs, which are little smarter than animals. The Constructs do not seem to share brainpower, like Network CPUs, but rather use the psychic network as a means of simultaneously, collectively sharing and storing information, sensory input and most likely as a means of receiving and transmitting orders. The experiences and recieved commands of one creature in a network are instantly, or near-instantly, received by every other. However, network activity seems to be taken in, transmitted and processed in a completely subconscious fashion, as no Mortis creature has ever shown any discernable signs of response or activity due to interaction with the network.