Ilona

"Meet Ilona, a member of the Sentinel Task Force. Cool and aloof, Ilona is not much for conversation and she doesn't need to be - her skills as a Tier One operator do the talking for her. Trained as a sniper in the Russian Spetsnaz Special Forces, she now uses her exceptional abilities for the ATLAS Corporation."

- Ilona description on the official Call of Duty website

Ilona is a major character in Call of Duty: Advanced Warfare. A sniper trained by the Russian Spetsnaz Special Forces, Ilona puts her skills to use under employment by the Atlas Corporation.

Background
As mentioned by her description, Ilona used to be a sniper for Spetsnaz, but was later employed by ATLAS Corporation.

Mitchell Joining Atlas
Ilona is first seen in "Atlas", training at the shooting range in the ATLAS HQ building before leaving, as Jack Mitchell and Gideon arrive so Mitchell can train.

Hunting Hades in Santorini
Ilona later interrogates Dr. Pierre Danois in order to find out where Hades is. Ilona manages to get information about Hades out of Danois and pinpoints Hades location in Santorini, Greece, where Hades is meeting with his top advisors.

Ilona appears in "Manhunt" where, along with Mitchell, she tracks KVA men in order to locate Hades, the leader of the KVA terrorist group, who organized a meeting in the area. When Hades attempts to escape after the ATLAS team led by Gideon was led into a trap, both Mitchell and Ilona decide to plant bombs on the convoy's way. As they attempt to drag Hades out of his vehicle, a KVA SUV arrives and attempt to run over Mitchell, only to get him stuck behind the car. Ilona then engages in a fight with Hades, only to be saved by Mitchell who succeeded to grab a knife and stab him in the throat. Shortly before dying, Hades said "Irons knows." and gives Mitchell a data chip before dying.

Leaving Atlas with Mitchell
Ilona then proceeds to analyze the chip and discovers that Irons executed the Technologist that Mitchell and Gideon previously saved after he warned Irons about the KVA's intention to attack nuclear plants, a warning Irons ignored, proving that Irons deliberately allowed the attacks to occur to improve Atlas' reputation. As Ilona calls Mitchell and Gideon to show them her discovery, ATLAS men arrive in the room and put both Mitchell and Ilona under arrest. However, Mitchell succeeds to kill one of the guards, take his gun and kills the second one before he could kill her. Mitchell and Ilona then escape the city, as they are guided by an anonymous man, who turns out to be Cormack, a U.S. Marine and former squad mate of Mitchell, who now leads the Sentinel Task Force, a U.S.-led multinational special ops team. As Mitchell and Ilona leave ATLAS, they decide to join Cormack and the group starts initiating ops against Atlas.

Defection to Sentinel, Irons Personal Estate and Antartica
After Mitchell and Cormack breached into Irons' private residence in Bangkok to discover that ATLAS is using a bio-weapon known as "Manticore", Mitchell, Ilona and Cormack attempt to recover a sample of the WMD after they crashed a cargo plane containing it in Antarctica. At the end of the mission, they are captured by ATLAS soldiers, only to be saved by Gideon, who joins the Sentinel Task Force as well.

Final Attack on Atlas
Later, Ilona, along with Mitchell, Cormack, and Gideon, are part of the Sentinels' attack on New Baghdad, in order to attempt to arrest Irons. However, the ATLAS triggers a Manticore attack in downtown, which does not affect Mitchell, Ilona and Gideon, due to their past as ATLAS soldiers and were thus inoculated, and Cormack, who was out of the attack's area of effect. They are, however, captured by ATLAS as Irons makes a victory speech to his soldiers and the citizens of New Baghdad.

Incarceration
All four are brought to a ATLAS prison, where Mitchell lose control of his prosthetic arm after Irons smashed it, and Cormack is heavily wounded by a gunshot. Ilona and Gideon succeed to kill the two guards protecting the cell, and proceed to rescue Mitchell and Cormack. During the level, a blast door splits the group, Ilona being forced to escape with the wounded Cormack while Gideon and Mitchell proceed to wipe out most of the guards. Ilona seize control of a truck and all four escape the ATLAS men. On their way to a safe point, she tries to rescue Cormack, however, due to large blood losses, he dies. Mitchell, Ilona and Gideon then swear to kill Irons.

Stopping Irons
In the last level, she guides Mitchell and Gideon through the ATLAS compound, as the Sentinels attempt to stop ATLAS from launching a missile full of Manticore towards the United States. The mission is successful, as both Mitchell and Gideon succeed to prevent the launch, and Mitchell manages to kills Irons.

Trivia

 * In the mission "Atlas", Ilona's name is displayed on the scoreboard at the shooting range, the grenade practice field and the assault drone range. She ranks at #1 in all three scoreboards.
 * Should Mitchell beat Ilona's score at the shooting range, she would comment "Shit. Where did this guy come from?"