

The Necromorphs are controlled via the Markers by a group of entities known as the Brethren Moons, which are massive, highly intelligent beings created after a Convergence Event is initiated by a Marker. They are believed to be the heralds of humanity's ascension by certain Unitologists and individuals suffering from Marker Dementia, but on a more practical level, they are the extremely dangerous result of the exposure of dead tissue to the Markers' signal. The sole purpose of all Necromorphs is to acquire more bodies to convert and spread the infection. The resulting creatures are extremely aggressive and will attack any uninfected organism on sight. There are some plot points that are "spoiled" if you go the chronological route, but that mostly happens if you read works set prior to the events of Dead Space (the main game) before playing it, but since you have played it already I'd say you can go either way.Necromorphs are mutated corpses reshaped into horrific new forms by a recombinant extraterrestrial infection derived from a genetic code etched into and transmitted by the Markers. Order of publication is usually the way to go for most media, as that is how the creators "meant" them to be presented to you. In my opinion, either play/read/watch it all in chronological order, or by date of publication, which I've put in parentheses after each work. Dead Space 2: Severed (DLC, 2011 takes place at the same time as Dead Space 2).Dead Space: Extraction (game and comics, 2009).Dead Space: Downfall (film, 2008 takes place at the same time as Extraction).Here's the chronological order of events in all Dead Space media, from my memory and this timeline on the Dead Space wiki.
