In the Mass Effect universe, billions of inhabitants occupy the galaxy. Along with humanity, a diverse collection of alien races also call the Milky Way their home. With so many individuals, it's guaranteed there will be a mix of both good and bad apples in the bunch.
Not every person Commander Shepard meets in Mass Effect: Legendary Edition is forthcoming about their intentions. In fact, few are always entirely honest with the player. Whether for good or ill, these NPCs believe it's in their best interests to keep their real motivations hidden. Ultimately, it's up to the player to decide how to deal with these less-than-honest individuals.
10 Jahleed
The player can encounter Jahleed in the first Mass Effect inside the C-Sec offices on the Citadel. When approached, Jahleed explains that his former colleague, a Salarian named Chorban, is out to murder him. Jahleed is cagey about the details, but Commander Shepard soon discovers the truth.
It's revealed that Jahleed and Chorban actually stole a scanner from their workplace. With it, they plotted to scan the mysterious Keepers in an effort to learn more about them. Jahleed, however, betrayed Chorban and kept the data for himself. He now seeks to tie up loose ends by eliminating his former partner in crime.
9 Gianna Parasini
At first glance, Gianna Parasini is a simple secretary for the notoriously corrupt administrator of Port Hanshan, Anoleis. She can assist the player in obtaining a garage pass to leave the port by directing Shepard to Lorik Qui'in, a Turian executive with an ax to grind with Anoleis.
Eventually, Gianna reveals her true nature to Commander Shepard. She isn't a secretary at all, but rather an internal affairs agent investigating Anoleis. It turns out the administrator is rocking the boat at the port by levying excessive bribes on the corporations doing business there. Whether or not Shepard assists Parasini in her investigation is up to the player.
8 Anto Korragan
Omega is a pretty dangerous place, filled with all sorts of criminal elements. In Mass Effect 2, the player may come across Ish, a shifty Salarian who wants Shepard to deliver two packages to him. One of these packages reveals something quite damning about Anto Korragan, a Batarian bodyguard for Aria T'Loak.
In addition to his bodyguard duties, Anto has been performing freelance mercenary work behind Aria's back. Ish seeks to leverage this information against the Batarian. If the player informs Anto of Ish's intentions, the vengeful bodyguard kills the Salarian to keep his double-dealings a secret.
7 Maya Brooks
Maya Brooks is one of the central characters of the Mass Effect 3: Citadel DLC. She presents herself to Commander Shepard as an overly nervous and awkward Alliance officer. Ostensibly, Brooks seeks to warn Shepard about someone trying to hack the Commander's private accounts.
Brooks turns out to be anything but an innocent intelligence officer. She is actually an ex-Cerberus operative as well as a fanatical believer in humanity's supremacy. Brooks's real intentions are to steal a Cerberus-created clone of Commander Shepard, thus appropriating the real Shepard's identity.
6 Nassana Dantius
Nassana Dantius is an Asari diplomat who seeks out the player's aid in the first Mass Effect. She explains that her sister, Dahlia, has been kidnapped by mercenaries. Despite paying the ransom, Dahlia hasn't been returned. Nassana tasks Commander Shepard with rescuing her sister from the kidnappers.
The whole story turns out to be a clever ruse. Dahlia isn't a victim, but in fact, the leader of the mercenary band. Dahlia's criminal activities are a source of embarrassment for Nassana, who manipulates Shepard into assassinating her sister. When the job is done, Nassana feels little remorse for ordering Dahlia's murder.
5 Donnel Udina
Commander Shepard deals extensively with Donnel Udina throughout the Mass Effect trilogy. Originally, he is the human ambassador on the Citadel. Through the player's actions, Udina can also become the Council representative in Mass Effect 2. By the time of Mass Effect 3, he is one of the most powerful politicians in Citadel Space.
Udina's desperate preoccupation with saving Earth in Mass Effect 3 prompts him to make a deal with the devil. He agrees to help Cerberus instigate a coup against the other members of the Council to safeguard humanity's interests. The plan ultimately fails, thus revealing Udina's actions as a traitor.
4 Harkin A.K.A. "Fade"
Harkin is a slimy and disgraced C-Sec officer, one of the first humans to fill the post. His corrupt reputation is well-known across the Citadel, while the downward spiral of his career is almost complete. Nevertheless, by the time of Mass Effect 2, Harkin manages to reinvent himself, and not in a positive way.
Garrus's hunt for information during his loyalty mission leads him to a criminal with the alias "Fade." This individual is revealed to be Harkin. After finally being fired from C-Sec, Harkin became a full-blown racketeer who now openly flaunts the law.
3 The Leviathans
Out of all the alien races, none are perhaps more mysterious than the Leviathans. An aquatic race of squid-like beings, the Leviathans predate the Reapers and Protheans. As such, they believe themselves superior to all other races. However, the rise of the Reapers forced the Leviathans into hiding to escape the former's destructive cycle.
What the Leviathans seek outside their own survival is a mystery. What is known is that their desire to preserve all life in the galaxy backfired. The Leviathans' noble efforts unintentionally led to the creation of the Reapers, a race of biomechanical dreadnoughts who seek to exterminate life every cycle in order to "save" it.
2 Dr. Saleon
Dr. Saleon is a Salarian geneticist who, for all intents and purposes, appears as a legitimate scientist. Through the player's conversations with Garrus, however, it's explained that Dr. Saleon is far from a respectable member of the scientific community.
Dr. Saleon is actually a mad scientist who conducts horrific biological experiments on his unwilling subjects. His method is to grow cloned organs inside the victims' own bodies before selling them on the black market. When confronted, the crazed Salarian maintains his innocence to the very end.
1 The Illusive Man
The Illusive Man is, without a doubt, an individual of many hidden agendas. His efforts to solidify humanity's supremacy over all other species are rarely brought to light. The Cerberus organization is his creation. Originally an Alliance black-ops division, in reality, Cerberus is a fanatically pro-human terrorist organization.
The Illusive Man views the Reapers both as a threat and as an opportunity. Although aware of their desire to wipe out humanity, the Illusive Man also believes the Reapers possess the means of making humanity the dominant race in the galaxy. Ultimately, this misguided assumption leads to the Illusive Man's downfall and his subsequent indoctrination by the Reapers.