Selene is the main character of the "Underworld" film series, portrayed by actress Kate Beckinsale. She is a vampire warrior who fights against the lycans (werewolves) and is one of the most skilled fighters among the vampires.

In the first film of the series, "Underworld," Selene is introduced as a fierce and determined vampire who is dedicated to hunting down and killing the lycans who she believes killed her family. She is highly skilled in hand-to-hand combat, as well as with a variety of weapons, including guns, swords, and knives. She is also an excellent tracker and is able to sense the presence of the lycans from great distances.

Selene is known for her iconic black leather bodysuit and her sleek, dark hair. Her appearance, along with her fighting skills, have helped to make her one of the most recognizable and beloved characters in the action-horror genre.

Throughout the "Underworld" series, Selene's character develops as she discovers the truth about the war between the vampires and lycans and her role in it. She becomes embroiled in a complex web of power struggles and betrayals, as well as personal relationships, including a romantic relationship with a human, Michael Corvin (Scott Speedman).

Overall, Selene is a highly skilled and determined character who is willing to do whatever it takes to protect her kind and to stop the lycans. Her character has been praised for breaking stereotypes about women in action films and for providing a strong and capable female lead.