The Humans
Isaac Clarke
Isaac Clarke started as a normal, everyday engineer of the Concordance Extraction Company (CEC). He is sent to investigate a communication blackout on the Ishimura, a planetcracker–class starship where his girlfriend, Nicole Brennan, was stationed. He discovers the crew had been murdered after finding a mysterious artifact called the "Marker" on Aegis VII. Worse, their bodies had been turned into grotesque, rampaging "Necromorphs." He finds Nicole but later learns she is merely a figment of the Marker's dementia and has been dead since his arrival. Isaac destroys the Marker and most of Aegis VII. A disturbing final visage of Nicole leaps at him as he barely escapes with his life.
Three years later, Isaac awakens with amnesia on the Sprawl, a giant metropolis orbiting Saturn. His encounter with the Marker on Aegis VII left codes in his head of how to build another Marker. In the middle of a fresh Necromorph outbreak, Isaac must solve the crazed ramblings of both a fellow patient and his dead girlfriend in order to reach the Government Sector, all while being hunted by the government and the Church of Unitology.
Nicole Brennan
Isaac Clarke's girlfriend, Nicole Brennan was the chief medical officer aboard the USG Ishimura at the time of the Aegis VII incident. In order to avoid falling victim to the gruesome murders unfolding around her, she took a lethal injection to end her own life. Her ghost reappears to Isaac on several occasions in Dead Space, seeming to help him end the outbreak on Aegis VII. In Dead Space 2, she appears in very disturbing forms, taunting Isaac with his survivor's guilt, driving him toward the final mystery of the new Marker aboard the Sprawl.
Nolan Stross
Nolan Stross is a patient in the psyche ward on the Sprawl. His encounter with the Aegis VII Marker was catastrophic, causing him to kill his wife and child in a fit of dementia, which has since left him in a state of psychotic denial. It also left him with codes in his head on how to build another Marker. Stross is more advanced in his dementia than Isaac, and his garbled memories hold the key to destroying the Marker—if he can last long enough.
Ellie Langford
A fellow CEC employee, Ellie is a Class 4 heavy equipment pilot and is at least as smart as Isaac. She is tough enough to hold her own in the Necromorph outbreak, and even views people as a liability under these conditions, including Isaac. Eventually she comes to work closely with Isaac as they struggle to survive the escalating chaos on the Sprawl.
Hans Tiedemann
Hans is the director of administration for the Sprawl, and his family has been in charge of the Sprawl for generations. His life's work has been to sustain and grow the community, even as it fell on hard times after the Ishimura incident on Aegis VII depressed all planetcracking activity—the Sprawl's main source of income. Tiedemann took drastic measures to keep the Sprawl alive, including making a deal with the government he would later regret—a deal that involved a highly secretive project involving Marker research.
Daina Le Guin
This mysterious woman is helping Isaac to escape and is communicating with him to help get him to safety. He has no other choice but to follow her.