Legal Name: Theresa Cassidy
Place of Birth: Mayo county, Ireland
Base of Operations: Xavier’s
Terry has had very basic hand to hand training from Black Tom and Juggernaut.
Powers (if applicable):
Siryn possesses sonic powers similar to those of her father Banshee, although she is able to use her powers in ways that he apparently could not. Siryn is a Alpha-Level mutant.
Audiokinesis: ability to create various sonic effects through the combined action of her vocal cords and limited psionic powers which can only be used in conjunction with the sounds she produces.
• Sonic Scream: Siryn can cause her vocal cords to vibrate over a wide range of sonic frequencies and produce a volume of sound ranging up to at least 140 decibels. Siryn has thus the ability to shatter solid objects with a sonic scream
• Flight: Siryn can use the sonic vibrations of her scream as a carrier wave.
• Sonic Lance: By focusing her sonic vibrations while screaming into an intense beam. This is used as a sort of "battering ram" that can stun or even destroy most solid objects.
• Sonar: can use her sonic powers as a form of sonar. By sending out a precise, pure note and listening to the returning, altered wavefront of the note, she can evaluate her surroundings in total darkness with varying degrees of resolution.
• Sonic Null Field: can project a field of silence in a area making no sound reach outside the area or no sound outside the area in
• Sonic Amplification: can amplify sound carrier waves allowing her to hear conversations or noises from far off.
• Sonic Shield: can tighten sound waves around himself or others near her, making a barrier against outside attack.
• Vocal Disorientation: ability to change someone’s balance, by affecting their equilibrium using her sonic scream
• Vocal Trance: ability to subtly influence peoples subconscious mind by changing the tones and vibrations of her voice using sonics, the effects tend towards blatant hypnosis.
• Vocal Unconsciousness: ability to affect the fluid in someone’s ear causing the person to go unconscious.
• Siren's Song: ability to influence human beings with a certain pitch of her voice, causing them to fall in love with her without regard to gender or sexual orientation.
• Sound Immunity: Siryn's hearing and equilibrium are unaffected by the effects of her scream and similar abilities.
Superhuman Vocal Stamina: Her vocal cords are tremendously strong, so that she can produce sonic effects through screaming constantly for hours at a time without noticeably tiring or injuring her vocal apparatus. Siryn’s vocal cords and the interiors of her throat and mouth are also superhumanly tough, so that the intense pressures and constrictions that she produces do not cause her any injury.
Special Limitations: Terry is unable to use her powers if she is unable to produce any sound with her vocal cords.
Source of Powers (if applicable): Mutation.
Weight 115 lbs (52.2 kg)
Unusual Features None
Theresa has a difficult time controlling her emotions and is quick to anger. She has a difficult time being independent after relying on Black Tom. After he was arrested, she started to learn how to be independent. Terry is stubborn and headstrong. She will generally decide on a course of action and following it, not thinking ahead or of the consequences. She has a habit of forming relationships with men who are bad for her. Her uncle Tom was the first and then she had a series of bad relationships with men after her uncle was arrested.
Terry is hesitant about using her powers and does not know the full range of what she can do with them.
Theresa Cassidy is the mutant daughter of Sean Cassidy, the mutant who was to become known as the Banshee, and Maeve Rourke. Soon after his marriage, Sean Cassidy, an Interpol agent, was sent on an undercover anti-terrorist mission for many months, not knowing when he left that Maeve was pregnant. Shortly after Theresa's birth, Maeve was killed in an IRA (Irish Republican Army) bombing along with a number of other people. Those who knew of Theresa's existence assumed that she too had been killed in the explosion and never told Sean Cassidy that Maeve had had a daughter. Sean was so filled with anguish when he returned and learned of Maeve's death that he left threw himself into a series of highly dangerous missions in order to lose himself in his work. Eventually this led to his resignation from Interpol and his later involvement with SHIELD.
Unknown to Sean, the baby Theresa had been found after the explosion by his cousin Black Tom Cassidy who, suspecting that she might be a superhumanly powered mutant as he himself and her father were, decided to raise her secretly himself. Theresa's sonic powers emerged at puberty, and a few years later Black Tom began coercing her aid in committing crimes. At one point during high school, Theresa developed a drinking problem.
However, Theresa's heart was never in a life of crime, and she pursued it because the man who raised her, Black Tom, ordered her to do so. Eventually Theresa accompanied Black Tom and his partner the Juggernaut to San Francisco. There, employing the name Siryn, she battled the original Spider-Woman heroine and several of the X-Men. This conflict ended in Black Tom's temporary capture. While in custody, Black Tom gentlemanly exonerated Theresa of responsibility for his crimes and wrote to Sean explaining who she was. Theresa went to live with her father, who had since retired back at Cassidy Keep.
Sometime afterward, Theresa lived for a while at the Muir Island mutant research facility owned by scientist Moira MacTaggert. There she met and developed a romantic relationship with Jaime Madrox a.k.a. the Multiple Man. At one point, she and Madrox helped to track down the young mutant Sunspot, which led to the mutants joining briefly the group known as the Fallen Angels at the behest of the mind-altering alien Ariel. Once Ariel's scheme was discovered, the Theresa, Madrox, and Sunspot returned to their respective homes.
Later, Theresa learned of an attempt by Black Tom and the Juggernaut to bomb the World Trade Center in New York, and she joined the formative group of mutants known as X-Force in defeating them. She remained alongside the team for a long tenure, and eventually grew to become Field Leader during the absence of their former leader, Cable. On a solo adventure, Theresa encountered the mercenary Deadpool when both were tracking down activities of Black Tom. The two developed romantic feelings toward one another, but parted company.
During her time with X-Force, Theresa's teammate Warpath developed a crush on her, and later he helped Theresa recover from a relapse into alcoholism. At this point, Deadpool tried to reenter her life, but did not want to deal with her alcoholism.
More recently, during a clash between X-Force and the villainous New Hellions, Theresa's vocal cords were severely damaged, causing her to lose her voice as well as her powers. Taking a leave of absence from the team, Theresa adjusted slowly to life without her powers, visiting with an aunt. Soon, however, Theresa walked into an antique store where the owner put a necklace on her. Theresa immediately began to talk again and flew off, the obvious victim of a possession, similar to the type performed by the deceased villain Malice.
Later, Theresa encountered Deadpool who managed to get her to an organization that was able to heal her using the mutant healing power of their captive, the X-Men's Wolverine. Wolverine was upset at Deadpool, even after Theresa broke out of her healing tank, but Terry stood by Wade and flew off with him. What became of her possessor is unknown. Theresa returned to X-Force and adventured alongside them for some time.
More recently, Banshee founded a mutant team, the X-Corps, as a paramilitary force that could police the mutant community. The team recruited several known villains and soon they embarked on a rampage through Paris until the X-Men were able to defeat them. Even so, Banshee was left wounded and the X-Corps was disbanded. Feeling the need to help atone for her father's debacle, Theresa offered her services to the X-Corporation, a clandestine extension of the X-Men operating as mutant champions on a worldwide scale.
Siryn is currently a teacher at Xavier’s Institute of Higher Learning.