He was portrayed by actor Stephen Nichols from July 1996 until October 16, 2003.
Stefan is the second son of villain Mikkos Cassadine—who once attempted to freeze the world with a weather machine in the famous 1980s Luke and Laura "Ice Princess" storyline—and his equally evil wife Helena.
Stefan first came to Port Charles in 1996 with his teenage nephew Nikolas Cassadine, the secret son of Laura Spencer and Stefan's older brother Stavros. The Cassadines are descended from a titled, aristocratic Russian family who fled to Greece following the 1917 Russian Revolution. Stefan had raised Nikolas since infancy after Laura had escaped the captivity of Stavros and been forced to leave Nikolas behind, after Stavros was presumably dead after falling down a flight of stairs, and after Helena murdered Laura's mother when she tried to contact him.
Stefan battled his mother Helena Cassadine for control of Nikolas and control of the family company and was official head of the family by the time Nikolas was seven. His mother, emotionally abusive to him during his childhood, viewed him as weak and soft, which he was only in comparison to the more homicidal members of the Cassadine family. Helena strongly favored his older brother Stavros and alternately ignored and belittled the more sensitive Stefan. Stefan loved and protected Alexis Davis, who was raised as his first cousin but later turned out to be his half-sister, both children of Mikkos. He paid for her to attend boarding school in the United States as a teenager and encouraged her to go into the legal profession.
However, he also dominated her and expected complete loyalty and obedience from her. Alexis was charged with doing much of the legwork for "Timoria", Stefan's planned vendetta against the Spencer family and General Hospital, both of which Stefan blamed for the presumed death of his brother Stavros. In their first years on the show, fans detected romantic chemistry in Stefan's scenes with Alexis. Stefan expressed disapproval of Alexis' relationship with Ned Ashton and she later went to great lengths to break up his engagement to Katherine Bell, whom she disapproved of. Fans of the romantic pairing called themselves the "Gutter Rats", though no actual romantic relationship was ever alluded to in their scenes together.
Laura Spencer contacted Stefan after her baby daughter Lulu Spencer was diagnosed with aplastic anemia and was in need of a bone marrow transplant from a matched donor. Nikolas turned out to be a match. True to the love-hate relationship Stefan always had with Laura, Stefan forced Laura to beg for her daughter's life. He then allowed Nikolas to donate the life-saving bone marrow to his sister. At the same time, Stefan launched his Timoria plot, to exact revenge on Luke and Laura for (presumably) killing his brother, Stavros, while he was attempted to rape Laura Spencer fifteen years prior. Stefan later married Luke's sister Bobbie Spencer as part of his revenge plot against the Spencers. The marriage ended in divorce after Stefan caught Bobbie investigating his actions against the Spencers.
In the intervening years, Stefan had an affair with and later became engaged to Katherine Bell. This relationship was derailed for a time after his "cousin" Alexis produced proof that Katherine was Stefan's half-sister Natasha. This was eventually exposed as a falsehood, when it turned out that Alexis was the real Natasha. This revelation rocked Stefan and he reacted as a true Cassadine. Stefan banished Alexis, but eventually forgave her. Katherine fell off a parapet during her engagement party to Stefan, the victim of a failed attempt to murder Helena by Luke and Alexis. Katherine was rescued by Helena Cassadine and restored to health, but died in a second fall from the parapet (this time assisted by Helena) soon after her return.
Meanwhile, Laura was harboring a secret about Nikolas, which strained her relationship with her husband and family. Eventually, Luke discovered that she had slept with Stefan and believed that Stefan, not Stavros, was Nikolas' father, and had lied to him about it. Meanwhile, Stefan had to face Nikolas about the secret that Stefan, too, had kept. Nikolas lashed out at Stefan, moving out and depending heavily on his brother, Lucky Spencer, and his friend, Emily Quartermaine, for support. Stefan did not approve of Nikolas's choices for companions, feeling that they were below his stature as a Cassadine. In particular, Stefan felt that Nikolas should always be wary of Spencers, and not trust them as he had come to trust Lucky. Eventually the two reconciled. Nikolas had always loved Stefan like a father, after all.
DNA testing later proved that Stavros was actually Nikolas' father, much to Stefan's bitter disappointment. The damage was already done to Luke and Laura, however, and they divorced. Shortly before Luke and Laura divorced, Stefan and Laura began a relationship, and Stefan felt hopeful that he could regain his relationship with Laura, the woman he had so loved and hated over the years. Unfortunately, their relationship ended bitterly, after Stefan learned that Laura's presumed dead son, Lucky, was alive, and temporarily withheld the information from her. Laura eventually learned about this from Luke, and violently confronted Stefan. Laura could not forgive him for the lie, and Stefan finally accepted that he and Laura had no future.
Stefan later fell in love with Quartermaine cousin Chloe Morgan and was framed for her murder when his back-from-the-dead brother, Stavros, killed her. The plot was eventually revealed and Stefan was cleared.
He appeared more aggressive and continually more deranged and desperate in his final year on the show. Stefan returned to the show after an absence. He had plotted an arranged marriage for Nikolas with Lydia Karenin, a wealthy Russian heiress, to restore the Cassadine family's wealth. He ordered Nikolas to marry Lydia, but Nikolas was reluctant to follow through. Stefan attempted to kill Nikolas's real love, Emily Bowen-Quartermaine, but pushed Lucky's girlfriend Summer (a Laura look-alike), off a cliff by mistake. His secret was well hidden, though, he thought.
Stefan's loan from Lorenzo Alcazar was due (this loan transpired as Stefan re-entered the show); Stefan and Lorenzo's henchmen fought quite a bit with him in his final weeks. At this time as well, Luke Spencer kidnapped and put Stefan on "trial" in front of the entire Port Charles television audience, taped by Dillon Quartermaine. Luke intended for Stefan to admit to the attempted murder of Emily Bowen-Quartermaine and actual murder of Summer Holloway. Stefan apparently died after he was burned (and disfigured) and later stabbed in a knife fight with Luke Spencer.
Luke was arrested for Stefan's murder but was released when Stefan's suicide note was found, where Stefan admitted that he had set Luke up for his staged "murder."
Kidnapped Laura's mother, Lesley Webber, and held her captive for years
Poisoned his mother, Helena Cassadine and held her captive in a paralyzed body for months
Faked his own death and kidnapped Chloe Morgan, making her think it was Helena's doing, and held her captive on the Cassadine island while trying to use her psychic dreams to bring down Helena
Paid Darius to kill Emily Quartermaine [Jun 2003]
Blackmailed Lydia Karenin [Jun 2003]
Assaulted Lydia [Jun 2003]
Attempted to kill Lorenzo Alcazar to cancel a debt [Sept 2003]
Kidnapped Lydia Karenin and held her hostage [Oct 2003]
Creators: Richard Culliton · Carolyn Culliton ·Wendy Riche Executive Producers:Wendy Riche (1997-1999) ·Julie Hanan Carruthers (1999-2003) Head Writers:Carolyn and Richard Culliton (1997) ·Lynn Marie Latham (1998-1999) ·Scott Hamner (1999) ·Karen Harris and Jonathan Estrin (2000) ·Karen Harris (2000) ·Karen Harris and Barbara Bloom (2000) ·James Harmon Brown and Barbara Esensten (2000-2003)