Commander Shepard - The main protagonist of the first game, Shepard is killed during the opening sequences of Mass Effect 2 and is later resurrected by the pro-human organization, Cerberus. Shepard is sent on a mission to hunt down the Collectors, who have been abducting whole human colonies and are suspected to be working for the Reapers.
Illusive Man - The ruthless and mysterious leader of the Cerberus organization, the Illusive Man is responsible for the funding of Project Lazarus - the revival of Commander Shepard. Little is known about the Illusive Man, except that he is apparently extremely wealthy. He forms an alliance with Shepard, providing guidance throughout the game as Shepard investigates the disappearance of several human colonies.
Grunt - A prototype krogan super-soldier, he is the brainchild of the krogan Warlord, Okeer. Bred and programmed with the memories and skills of various powerful krogan and having undergone extensive genetic engineering, Grunt is considered the most "perfect" example of the krogan species. However, he has no clan and little knowledge of krogan customs and tradition, leaving nothing to act upon except his instincts to fight.
Mordin Solus - A brilliant salarian scientist, yet also a competent soldier due to his membership in the Salarian Special Tasks Group earlier in his life, Mordin Solus is found on Omega and possesses a hyperactive and eccentric personality. Mordin believes in acting in the best interests of the galaxy; his scientific work is governed by strong moral standards and unquestionable respect for all forms of life.
Samara - An asari Justicar, Samara is highly skilled in her use of biotics. A member of a highly respected and feared monastic order, Samara has forsworn all possessions and family to fight for absolute justice. She is on a quest to track down her elusive daughter Morinth, who has been killing innocents for hundreds of years by burning out their nervous systems through sexual intercourse.
Jacob Taylor - Jacob Taylor is a former Alliance soldier with biotic abilities. He joined Cerberus after viewing the bureaucracy of the Alliance as hampering the ability of humanity to survive. Taylor is highly respectful of Shepard due to their shared background in the military. Thirteen years before, he had cut ties with his father, who was a First Officer of a lost spaceship, the Hugo Gernsback.
Miranda Lawson - Genetically modified to perfection by her father, Miranda Lawson is the top Cerberus agent on board the Normandy and Shepard's second in command. Driven and devoted to the Cerberus cause, she is often viewed as cold and callous by other Cerberus agents. Providing military and tactical support, Lawson also acts as the liaison for the Illusive Man.
Thane Krios - A drell assassin who is dying of a lung disease exclusive to his species, Thane Krios joins the team in an attempt to provide a purpose to his life and atone for his past actions. An expert assassin, he also possesses powerful close-combat biotics. His wife was murdered many years ago by batarians in an attempt to trap him. This forced him to withdraw from his son, Kolyat, an event that still haunts him.
Jack/Subject Zero - The product of a Cerberus experiment to enhance human biotic ability, Jack carries a hostile personality that is the result of the torture and captivity she endured while she was imprisoned at a remote Cerberus outpost during her childhood. She later escaped and became involved in crime, murder, and religious cults, all in an attempt to gain an identity. She was later captured and imprisoned aboard the prison station Purgatory, where Shepard recruits her upon escaping captivity.
Tali'Zorah vas Neema/Normandy - Tali'Zorah vas Neema returns to the Normandy after a scientific study goes horribly awry and most of her team is taken out by geth. She joins Shepard once he rescues her from the assaulting geth force. She was later charged with treason by the quarian Admiralty Board for smuggling active geth for her father.
Garrus Vakarian - After the Normandy was destroyed, Garrus Vakarian went on to pursue a life of vigilantism. He made his way to the Omega space station, which is riddled with criminal syndicates, and earned the alias Archangel after sabotaging various criminal organizations. When Shepard finds him, Garrus is holed up in his base as three crime syndicates send waves of mercenaries to kill him. During the final onslaught he is injured by an attack from a gunship, leaving him with facial scars and damaged armor.
Legion - During a mission to recover an IFF transponder aboard a derelict Reaper, Shepard encounters a lone and damaged geth. This geth assists Shepard by eliminating several enemies and allowing Shepard to access the core of the ship, but is knocked inactive by several husks shortly afterwards. Upon destroying the Reaper core, Shepard brings the inactive geth to the Normandy with the option of sending the geth to Cerberus for research or reactivating it. If reactivated, the geth claims to be the first pure geth that Shepard has encountered, stating that all previous geth were "heretics" who supported the Reapers. As the Geth is not an individual persona and has a physical body that contains multiple runtimes, it identifies itself simply as geth until EDI decides to give it the name, Legion.
Zaeed Massani - One of two DLC party members, Zaeed Massani is considered to be the most ruthless and prolific bounty hunter in the known galaxy. He joins the Normandy's crew for the large payment in credits he would be receiving from the Illusive Man. Massani is secretly the co-founder of the Blue Suns mercenary organization, betrayed by his partner twenty years ago.
Kasumi Goto - The best thief in the galaxy, Kasumi Goto joins Shepard's team in return for his assistance in stealing a "graybox" - a hard drive encrypted through use of one's memories - that belonged to her former partner and lover.