Elena is the sister of Irina and Katya Derevko and was one of the KGB's foremost assassins, responsible for the murder of countless diplomats and politicians throughout Eastern Europe. She was described by her sister Irina as "volatile and quick-tempered". Considered the most ruthless of the Derevko sisters, Elena is the secret leader of The Covenant. She was first mentioned in the season three episode "Crossings" by Jack. She is not referenced again until the fourth season, when in "Welcome to Liberty Village" it is revealed that an unidentified Russian group is trying to find her.

Thirty years before Season 4, Elena disappeared and could not be found, even by Irina and around a year before Season 4, Arvin Sloane and Jack Bristow had been investigating Elena's whereabouts until Jack received a message from an old associate that led him to one of Elena's safehouses in Warsaw. Inside was detailed information on the lives of Sydney Bristow and Nadia Santos, her nieces, with evidence suggesting she had them under surveillance for at least a decade.

Soon Nadia's former caretaker Sophia Vargas arrived in Los Angeles claiming that her reason for coming to the United States was due to an attack by an unidentified group at her home in Lisbon, Portugal. They quickly assumed Elena was the responsible behind the attack, not realising that she was in fact "Sophia".

Under the alias of "Sophia Vargas", Elena used her former connection to Nadia to stay with her and Sydney to monitor their work for the CIA. She also monitored Nadia's conversations through a necklace equipped with a microphone.

She later hacked into Nadia's laptop and requested to move the Hydrosek, a deadly weapon, to an unsecured location away from APO. Elena and her associate Avian then stole the weapon before Nadia and Weiss could stop them, not realizing who the thief was.

In order to complete her endgame, Elena, fully aware of the fact that he would at some point double-cross her, also ordered the creation of "Arvin Clone", a corporal in the U.S. Army named Ned Bolger, who was captured and brainwashed to believe that he was, in fact Arvin Sloane, committing numerous criminal acts in the process, such as setting Irina up to appear as if she had contracted an assassin to kill Sydney.

Elena sent a team into the Department of Special Research to steal all the Rambaldi artifacts necessary to complete "Rambaldi's endgame". On the same night, she left Sydney and Nadia's house, saying that she had been informed by the Lisbon police that it was safe for her to return. Hours later, Hayden Chase entered the house and accused Nadia of working against the government and allowing the team to break into the DSR. It was at this point that Jack and Sloane began to realize that Sophia was Elena, which was backed by the microphone found in the necklace given to Nadia by Sophia.

Sloane deduced that Elena would go to Lazlo Drake with the Rambaldi artifacts. Sydney and Sloane went to meet him, but he was already dead. Sydney found a hidden camera and rewound the feed to see Elena talking with Drake. Before she could see where they planned to take the Rambaldi artifacts, Sloane tranquillized her and left. He met up with Elena in her office in Prague and offered his services to help complete her task. Jack discovered through Katya Derevko that The Covenant was a major terrorist organization set up by Elena in order to secretly acquire Rambaldi artifacts.

Dixon, Nadia and Sydney were sent on a mission to stop them. Dixon found Elena and Sloane, but Elena shot him before he could react. While in the hospital, Dixon told Sydney that he saw Irina Derevko before Elena shot him. It was discovered that Elena had used Project Helix to create a double of Irina, then through the use of "Arvin Clone" set up a hit on Sydney, sparking the events that led to the double's execution - to ultimately lead the intelligence/criminal world to believe that she was dead. The double was described as being an ardent follower of Elena Derevko, and fully aware of the fact that she was being set up to die.

The real Irina, however, was imprisoned by Elena, and tortured for her knowledge of a Rambaldi prophecy known as "Il Diluvio", the Flood. She was kept for eighteenth months in Prague, but moved to a remote location in Guatemala - Tikal. Sydney, Jack and Nadia located her through Lucian Nisard, and saved her from Elena's guards.

Elena and Sloane constructed a massive Mueller device over the Russian city of Sovogda which, in conjunction with the tainted water supply from The Orchid, infected the people of Sovogda and made them extremely aggressive. When Sloane learned that APO had sent a team into the city to stop them, he offered to head out with the team himself. While he was doing this, Elena began to transmit a subaudible frequency via the Russian mil-sat network to spread the infection worldwide. The second that the bombers were scheduled to destroy Sovogda, the frequency would be broadcast causing the effects of Sovogda to occur worldwide.

One of Elena's men found Nadia walking around the streets and brought her to Elena, who told Nadia that she never wanted to hurt her. She said that she always thought of Nadia as her daughter, then offered her a place alongside her. She showed Nadia a map of the world with pinpoints all over it, saying "the flood has begun, just a few will survive." Nadia refused to join her, saying that she would never kill Sydney as Rambaldi's prophecy had stated. Elena then injected Nadia with the tainted water, which infected her with the aim of forcing her to kill Sydney.

Elena noticed Sloane on the monitor. He was back and carrying a supposedly unconscious Vaughn, but as soon as they arrived in the base they began to shoot Elena's men. They were joined by Jack and Irina. They got to Elena and Irina knocked her to the floor with her gun. Sloane put Elena in a chair and Jack and Vaughn went to the computers to stop the mil-sat network from uploading the frequency. However, they could not retract the transmission. Elena told them that she had planned the attack for five years; it would not be that simple to stop her. Sydney managed to get into the main circuit board, but found a blue and a white wire. Irina did not know which to cut, and she asked Elena. When she refused to answer, she told Jack to start torturing her. Before he could do so, Elena told him to stop, and said to cut the white wire. Irina immediately shot Elena on the head and told Sydney to cut the blue wire.

Elena's Past with Nadia

Sydney and Vaughn discover footage of a very young Nadia being tested with Rambaldi fluid in a Russian bunker. Katya Derevko tells them Nadia was born to Irina in a Soviet prison after Irina left Jack. Sydney was born in 1975 and Irina left in late 1981. This means Nadia has to have been born in 1982. The footage proves Nadia was in Soviet custody for at least the first few years of her life. Conservatively, based on the footage, she could have been in Soviet hands until at least 1985.

Elena, as Sophia Vargas, tells Michael Vaughn the only time she met his father Bill was when he left Nadia in her care at the orphanage in Buenos Aires. However, Michael Vaughn locates Sophia's address in Lisbon through an encoded entry in a journal purported to have belonged to his father, which indicated Bill Vaughn had survived past 1979, when Irina Derevko was supposed to have killed him. Since this journal was revealed a forgery, there is no reason to believe information given by Elena supporting the authenticity of the journal was true.

Nadia ran away from the orphanage in 1992. The footage is fairly dark but it is possible she was as young as 10 when she ran away. She's in a dormitory with other girls of about that age. She's recruited by Roberto Fox when she's 17 or 18, which would make the year 1999 or 2000. She dies in circa 2007.

In this timeline, the only loose ends are how Nadia ended up at the orphanage in the first place and why the mercenary Roberts would tell Michael Vaughn his father was involved. Since the orphanage was headed up by Elena Derevko, the most obvious explanation is that Elena kidnapped her after she was taken from lrina and she simply lied to Vaughn about his father's involvement, and Roberts was paid to do the same.