Selene was born to a Hungarian family. Her father was a well-known architect who helped design a fortress for a general named Viktor. The fortress was actually a dungeon intended for the imprisonment of 'The' Lycan Elder, William Corvinus, condemned for his bloody and destructive behavior and a definite persona non grata for Viktor. After Lycans presumably killed her family, Selene was the only one left alive who had walked through the corridors of the fortress. However, she did not know that her family was slain by Viktor himself, and believed Viktor had saved her from the Lycans. That night her family was killed and she was made into a vampire by Viktor.
She became a Death Dealer, fighting against the Lycans for vengeance on the atrocities she believed they had committed against her family. She also exiled the Official Historian, Andreas Tanis, on Viktor's orders. Many years later (shortly before the events portrayed in Underworld) she became an object of romantic interest for Kraven, the Coven's regent, however she did not reciprocate his advances.
Selene appears to be very serious and bitter as she rarely smiles. She is proficient with many weapons, both medieval and modern. Modern firearms that she uses include the Walther P99 and a variety of automatic machine pistols. In both movies, she is seen jumping from a ledge from at least 100 feet in the air and landing without injury.
Selene frequently demonstrates superhuman physical abilities. She uses super strength to pin Michael against a wall several feet off the ground, performs spectacular leaps, and strikes her enemies with tremendous force. She kills younger Vampires with just a few blows. She takes a shotgun blast to the abdomen without flinching and manhandles four police officers as if they were rag dolls. She also has the ability to hold her breath for long amounts of time, as humans needed SCUBA to make an underwater dive in Underworld: Evolution. While she did it with one breath, she gasped for air when she reached the surface. After fortifying herself with some of Alexander Corvinus' blood, she is able to lift people with one arm and go toe to toe with Marcus, another Vampire Elder and actual first Vampire (not Viktor as he led all to believe), in his hybrid (half-bat) form. She has been slammed against stone walls, breaking the stones, but with no ill effects. By the end of the second film in the series, she is completely devoted to Michael, and he to her, and together they form a strong alliance against any who oppose them.
After a confrontation with the Lycan hitman Raze, she discovered what was supposedly a Lycan lair. She was angry when Kraven dismissed her claims, not knowing that Kraven was in league with the Lycan leader Lucian in a bid to take over the control of the vampire realm from the Elders. She tracked down Michael Corvin, who she believed the Lycans had an interest in. Against the sacred rules of The Vampire Covenant, she and Michael, who was infected with the lycanthropy disease, fell in love. She awakened Viktor from his deep slumber, believing that only he has the power to deal with the conspiracy between Kraven and Lucian. She then led a mass assault on the Lycans' underground bunker. After Michael was shot by Kraven, Selene was forced to infect Michael with her vampire strain, thus making him the first lycan-vampire hybrid. She also learned the truth about her family's killer from Kraven, and she struck Viktor down while the Elder was preoccupied with fighting Michael. She then retrieved Sonja's pendant, carrying on her legacy.
After Viktor's death, Selene and Michael went on the run from both Lycans and Vampires. She was confronted by Marcus, the last surviving Vampire Elder. As Marcus attacks her, Michael intervenes and battles him to protect her. After narrowly escaping Marcus and the sunlight, Selene and Michael take refuge in a warehouse. Selene finds that she has seen the pendant, that Marcus was trying to get, when she was a child.
In order to find out why Marcus was after the pendant, she sought out Andreas Tanis. Tanis told her the truth about her family's slaughter and revealed to her that, contrary to popular belief, Marcus, not Viktor, is the original vampire. He then set up a meeting for her and Michael with Alexander Corvinus, Marcus' father and the first true immortal.
Selene was angered at Alexander for not removing the threat his sons, Marcus and William, posed long ago. Alexander retorted by asking her if she would murder her own son. An interruption by Marcus in which Michael is seemingly killed also results in Selene's memories of the fortress to be taken by Marcus through her blood. Alexander, dying from his son's attack, told Selene that the only way to defeat Marcus and William would be to drink his legendary immortal blood, adding that she would become "The Future". Selene gained greater strength and new powers from Alexander's blood.
She and a squad of Alexander's Cleaners invaded William's dungeon, trying to stop the threat. They arrived too late, however, and Selene was forced to fight Marcus. Marcus was shocked by smelling his father's blood coursing through Selene's veins. Locking Marcus in William's dungeon, Selene discovered that William had infected all the Cleaners, who became Lycans themselves. On the verge of being overwhelmed she was saved by Michael, who was saved by his Hybrid powers. She fought Marcus once more, and the Elder drove his wing talon through Selene's chest. Selene, empowered by Alexander's blood, tore away the talon and drove it up Marcus' skull before throwing him into helicopter blades and killing him.
After she killed Marcus and Michael killed William, she discovered that she was able to stand in the sunlight, the pure Corvinus Strain from Alexander Corvinus fused with her vampire Corvinus strain, thus phenomenally enhancing her strength and healing to a level equivalent to that of a Vampire-dominant Hybrid, even being able to withstand direct exposure to sunlight, qualifying the classification of a true immortal. In the last scene, after Selene defeats Marcus, Michael watches as Selene discovers that she can now let sunlight fall upon her without harm. The only apparent side effect of her transformation was the pigment of her eye color from luminescent blue in her vampire form, which she had always had in her vampire form previous to drinking Alexander Corvinus's blood yet the colour after was much brighter.