The First Aegis VII Incident was an event that took place prior to the Dead Space game trilogy. The event was hinted at in the first game and minor details have emerged in various literary sources.
Taking place nearly two hundred years before the events of the first game, the barren planet of Aegis VII was selected by EarthGov to be a test bed for Marker experiments. A duplicate of the Black Marker discovered on Earth had been created and moved to the planet where EarthGov attempted to decipher the abnormal markings and glyphs etched upon the obelisk's surface. A number of experiments were carried out in an effort to effectively harness the energy that the Marker produced. However, these experiments resulted in the creation of a microbial life-form made from recombinant DNA which grew along with the Marker's field of influence.
The EarthGov personnel quickly fell victim to the manipulations of the Red Marker, resulting in anarchy as murder and suicide ran rampant across the planet. The deceased personnel were reanimated as Necromorphs and continued to spread by slaughtering whatever humans were still alive.
It is unknown if anyone from the original colony site survived the outbreak, but afterwards the Aegis Cluster was abandoned and declared off-limits. The Necromorphs left on Aegis VII joined together in a minor Convergence Event, forming the massive Necromorph entity that would become known as the Hive Mind during the second incident centuries later.