Helen Alexandros was created by Roy Thomas and Gene Colan, and her first appearance was in Wonder Woman #288, February 1982.
Major Story Arcs
Helen Alexandros was a former ballerina who had become bitter by the multiple rejections she suffered because of her plain, blemished face and overall 'ugly duckling' appearance. After a performance in an ancient Greek temple, she cried out to the gods and is answered by Ares. Ares reveals that she is descended from Helen of Sparta - daughter of Zeus and Leda and then asks if she is ready to accept her heritage. Helen agreed and was transformed into the Silver Swan, a beautiful woman capable of flight, super strength, and a swan song that could cause terrible destruction. Helena was limited to transforming for only an hour at a time and only as long as she served Ares, but was told that once she destroyed Wonder Woman, she would become the Silver Swan forevermore.
Helen infiltrates the life of Wonder Woman in many ways. As the Silver Swan she helps Wonder Woman apprehend a gang of bank robbers. Notably, a briefcase containing secret documents that she and Steve Trevor had with them disappears. Later on, when Diana and longtime companion Etta Candy discover that rent increase has made it necessary to take on a roommate, Helen Alexandros applies. They accept her right away and, having coincidentally found the lost briefcase, Helen returns it to Diana.
When Wonder Woman later attempts to return the briefcase, the Silver Swan attacks. She successfully defeats Wonder Woman in battle, but is not willing to kill her with witnesses around. She successfully convinces the others that she thought Wonder Woman was stealing the briefcase.
With the help of Captain Wonder (a villainous identity forced upon Steve Trevor by Doctor Psycho), the Silver Swan defeats Wonder Woman again. Falling in love with one another, the two of them decide to murder the captive Wonder Woman in front of the president of the United States. Ares appears and demands that they also murder the president. However, Steve Trevor breaks from Doctor Psycho's control and Wonder Woman is able to break free. She promptly defeats the Silver Swan and saves the president's life.
Disappointed, Ares withdraws his powers from the Silver Swan and she transforms back into Helen Alexandros.
Silver Swan (?)
A Silver Swan resembling a mix of Helena Alexandros and Vanessa Kapatelis was seen during Salvation Run as one of the villains exiled to a distant planet. She was on "Camp Luthor", a group following the leadership of Lex Luthor.
Later still, she was spotted during Final Crisis as a victim of the Anti-Life Equation. Briefly seen fighting Hawkgirl, it is unknown the overall part she played.
After the revelation that Vanessa Kapatelis had returned to university and graduated (with absolutely no signs of the Silver Swan cybernetics) the question is now proposed: is it a new Silver Swan seen during Salvation Run and Final Crisis? Is it Helena or Valerie?