NECROMORPH / BLACK MARKER

The Necromorph is the designation given to an alien microbe generated on Eagis VII by the Red Marker, a prototypical reverse-enginnered construct based on the Black Marker alien artefact that was discovered on Earth.
The strategy employed by the virus is the rapid transformation of deceased organims into Necromorphs, a process called "Recombination" which initiates a rapid mutation in the host body: with a series of violent convulsions, the spine elongates to accommodate a pair of grasping arms that burst from the abdomen; the shoulders are contorted, and long scythe-like bones extend from the wrists. Other mutations are largely variable, including short tentacles, large tumorous growths, and corroded flesh. This is the main form of Necromorph, but many others exist, including tentacled baby-like creatures and heavily mutated crawling variants. In addition to the vaguely humanoid Necromorphs, there also exists an extensive presence of some biological material far too large to have been formed out of human bodies, and which vary greatly in physical composition. The largest of these is the Hive Mind, which is easily thousands of feet long and telepathically controls all other infected organisms.
Source: Dead Space