Aegis VII is the seventh planet in the Cygnus system. It did not have oceans or islands, but only lakes. The planet had not fully lost its atmosphere at the time when it lost all its water, but there were still a few aquifers which were frozen or evaporated eventually, but not before the human race came in the USG Ishimura.
There was an artifact called the Red Marker on Aegis, which Humans had reversed-engineered from the Black Marker. It was placed there by the Earth Government or EarthGov to study it in secret. Before cracking Aegis 7, the Ishimura took the Marker from its pedestal. The marker genetically altered the DNA in the dead humans by a Carrier wave, turning any dead flesh into Necromorphs. An entity that telepathically controlled the Necromorphs, called the Hive Mind was exposed by the Ishimura's planet cracking operation. During the crack the colonies's communications system was jammed and by the time the Ishimura contacted them they discovered that almost everyone was killed by the Necromorphs. However two emergency shuttles reached the Ishimura, one had Colin Barrow who escaped with the corpse of his wife, who unknown to him, had been transformed by an Infector which carried the virus. The ship was quickly subdued by the Necromorphs.
Three people from the CEC named Isaac Clarke, Kendra Daniels, and Zach Hammond travelled to the Ishimura, due to a distress call. Only Isaac survived, but he was burdened with a severe case of dementia. He defeated the Hive Mind, but did not kill it. A (supposed) infant hive mind is later seen in Titan Station, a metropolis that is commonly called 'the Sprawl' in the shattered remains of Titan, a moon of Saturn.