Oleg Petrovsky

Oleg Petrovsky is a Cerberus general. He is an experienced and formidable military strategist, as well as a classical scholar with a deep knowledge of military history. Viewing the path that humanity is taking and the looming danger of the Reapers in that context, Petrovsky is concerned about humanity's future and strongly supportive of Cerberus' plans.

Background
As an Alliance corporal in the First Contact War in 2157, Oleg Petrovsky was forced to take command of his unit and proved his tactical brilliance by holding off repeated turian attacks for weeks. The war ended before his position was overrun, but not before Petrovsky had witnessed firsthand the brutality of the turian war machine. Despite being praised and promoted for his bravery, Petrovsky eventually found more common ground with Cerberus than the Alliance military. Over the years he became one of the Illusive Man's most respected operatives.

Mass Effect: Invasion
As Aria T'Loak defends Omega from the Adjutants, hostile Husk-like creatures unleashed on the station by a Cerberus transport ship, the Illusive Man dispatches General Oleg Petrovsky and Colonel Raymond Ashe to aid her in containing the threat. Petrovsky is in command of a powerful starship called the Elbrus, which he uses to decimate the remaining Adjutant-controlled Cerberus ships surrounding Omega.

When first encountered by Aria aboard the station, Petrovsky is euthanizing a turian who had been badly wounded by an attacking Adjutant. Aria accuses Petrovsky of butchering aliens, but as a nearby salarian transforms into an Adjutant, the general points out that what he is doing is a necessity; killing those who were attacked is the only way to stop them from transforming.

Petrovsky then asks Aria to gather together what help she can provide the Elbrus so that they can defend against the next wave of ships, which will likely have much better weaponry, until Cerberus reinforcements arrive. When Aria asks if he will make a last stand, like how he lasted against a turian assault for several weeks when he was a corporal, Petrovsky explains that the strategies he's using were chosen because the makers of those strategies lived. As more Adjutant ships enter Omega's space, Petrovsky vows to lift the siege.

The Adjutant ships quickly overwhelm those defending Omega. Petrovsky takes the Elbrus through the Omega 4 Relay, reasoning that they can be stopped at the source: Cerberus's Avernus Station. Petrovsky, Aria, and a Cerberus squad clear the station out, but Aria overexerts herself with biotics and passes out. The Illusive Man orders Petrovsky to restrain her and drop her off at a research station so that Cerberus can take over Omega virtually unopposed; without Aria's leadership, the fragile peace between Omega's gangs splinters, allowing Cerberus to move in. Petrovsky complies, but begins to express suspicions about how the Adjutants were released. He is not pleased with the possibility that so many of his men were lost to only further a ruse.

During the return trip to Omega, Aria breaks free and forces Petrovsky to take her back with him. Petrovsky warns Colonel Ashe in a coded message that the Elbrus has been compromised, but Ashe's preparations fail to catch Aria and she escapes into the station, where she quickly unites the gangs against Cerberus. In the following battles, Petrovsky and Ashe come into conflict, with the General appalled at Ashe's disregard for the safety of his own troops and civilians.

When he realizes that Cerberus has no hope of defeating Aria on her own turf, he comes up with a plan to get her to talk. Aria has a plan of her own and designs an ambush to distract Petrovsky's forces while she slips into the Afterlife Club to contact the Illusive Man. Thinking his superior had failed, Ashe triggers a trap in Afterlife: he remotely releases an Adjutant in the building to kill Aria. Petrovsky expresses outrage that Ashe would endanger Cerberus's troops and the station's civilians, but Ashe argues that they are acceptable losses. They struggle briefly before Aria hurls the Adjutant into them. It infects Ashe before Aria finishes it off. As his subordinate transforms, Petrovsky kills him to protect his men.

Now that he can speak with Aria, Petrovsky reveals that he has already won the battle for Omega. He had evacuated most Cerberus forces earlier so that the fleet surrounding the station could open fire and destroy it in the event it could not be secured. He gives Aria two options: she can continue to fight and be destroyed with the station she cares for so much, or she can accept exile and surrender Omega to Cerberus. Knowing that Petrovsky will back up his threat, Aria concedes. Petrovsky finally secures Omega for Cerberus. In his report to the Illusive Man, the General asserts that Aria was most likely killed and turned into an Adjutant, and Colonel Ashe is missing and presumed dead. He states that he hopes this victory will help spare the lives of his soldiers in future battles in the defense of humanity. Afterward, Petrovsky reflects on his last conversation with Aria and predicts that one day, she will return.

Mass Effect 3: Omega
Aria returns to reclaim her station, using a captured Cerberus cruiser to infiltrate the Cerberus blockade. Petrovsky realizes Aria's attack instantly as her ships come through the relay. He hails Aria's ship and advises her to turn back, revealing to having upgraded Omega's defenses. This proves to be true as the defense cannons easily cut through the Silaris armor of Aria's ship. However, Aria and Commander Shepard are able to board the station and disable its defenses.

Petrovsky spies on Aria's movements through security cameras during the initial stages of Aria's attack, determining that she is going to her bunker. He sends troops there to prevent them from getting in, but they are unable to stop her.

Petrovsky later appears via hologram at one of the main reactors, trapping Aria, Shepard and Nyreen Kandros in an enclosed force-field and smugly declares that he has beaten them. However, Aria and Nyreen manage to use their biotics to briefly open a hole in the force-field for Shepard to get to the reactor controls. Upon reaching the controls, the Cerberus general informs the Commander that shutting down the reactors to deactivate the force fields would endanger Omega's civilians. As Shepard grapples between cutting the power and rerouting it - which will take time and endanger Aria and Nyreen, Petrovsky questions the Commander's resolve to helping Aria, pointing out that she would sacrifice anything and anyone for her own selfishness. However, if Shepard is an Engineer, the Commander can use their omni-tool to reroute power quickly, which surprises him. Either way, the force-fields are deactivated and the trio survive. As Omega goes into a riot with civilians attacking their Cerberus oppressors, Petrovsky readies himself for the final battle.

As Shepard and Aria near Afterlife, where Petrovsky has set up his command post, Nyreen, alone, runs off ahead, directly into a group of rogue Adjutants. Nyreen sacrifices herself to destroy the Adjutants, enraging Aria, who charges into Afterlife. However, she runs right into a stasis trap set up by Petrovsky. The general then unleashes a hoard of perfected Adjutants along with a number of Cerberus soldiers upon Shepard. Shepard manages to free Aria from the trap and the two of them then proceed to defeat the Adjutants and the Cerberus troops. Without his last line of defense, Petrovsky surrenders and orders his remaining forces to stand down.

Aria and Shepard then confront Petrovsky. Though he offers to provide the Alliance with intelligence on the Illusive Man in exchange for amnesty, and reveals that he let Aria escape Omega in the initial Cerberus assault, a vengeful Aria assaults Petrovsky and starts strangling him.

Depending on Shepard's actions during the mission, she may relent at the last moment and hand him over to the Commander. Alternatively, Shepard can intervene and get Aria to spare him. Shepard can decide to spare the General, handing him over to the Alliance, or leave Petrovsky to Aria who kills him on the spot, delivering a slow, painful death as revenge for taking Omega. Shepard can also choose to execute Petrovsky by shooting him in the head.

If Petrovsky is spared, he contributes to the war effort. He is taken to an undisclosed location where the Alliance interrogates him for information about Cerberus's activities. He is cooperative, providing the location of a Cerberus base that the Alliance destroys, and Alliance officials are likely to grant him asylum.