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Theresa Cassidy (Earth-616)

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Theresa Cassidy (Earth-616)
Information-silkReal Name Theresa Maeve Rourke Cassidy
Information-silkCurrent AliasMorrigan [1][2]
Information-silkAliasesBanshee,[1] Siryn,[3] Terry,[citation needed] Sy,[citation needed] Theresa Rourke,[4] Tracy Cassidy,[citation needed] Screaming Mimi[5]
Information-silkRelativesLiam Cassidy (paternal ancestor, deceased);

Patrick Rourke (maternal grandfather, deceased);
Sean Cassidy (Banshee) (father, deceased);
Maeve Rourke Cassidy (mother, deceased);
Thomas Cassidy (Black Tom) (cousin);
Victoria Donnely (cousin);

Sean Madrox ("son", re-absorbed by Madrox)
Information-silkAffiliationFormerly X-Factor Investigations, X-Force, X-Corporation, Muir Island X-Men, Fallen Angels, ally of Black Tom & Juggernaut
Information-silkBase Of OperationsX-Factor Investigations Headquarters, New York City, New York; formerly Detroit, Michigan; Mutant Town, Manhattan, New York City, New York; Xavier Institute, Salem Center, Westchester County, New York; Adirondack Mountains, Camp Verde Reservation, Arizona; Murderworld; Beat Street Club, Manhattan, New York; Mutant Research Center, Muir Island, Scotland
Information-silkIdentitySecret Identity
Information-silkMarital StatusSingle
Information-silkOccupationPrivate detective; former adventurer, research assistant, criminal, student
Information-silkEducationBoarding school
Information-silkHeight5' 7"
Information-silkWeight130 lbs (59 kg)
Information-silkPlace of BirthCassidy Keep, County Mayo, Ireland
Information-silkCreatorsChris Claremont, Steve Leialoha
First Appearance

Quote1 My vocal cords are lethal. My estrogen level is berserk. Between Braxton-Hicks and my huge belly, I haven't slept in weeks. And I gotta pee...again. Free advice, Ms. Cooper. Never bet your life on what you think you know about a hormonal, sleep-deprived W.M.D. with a full bladder. Quote2
-- Siryn src


Theresa Maeve Rourke Cassidy is the mutant daughter of Sean, the mutant who was to become known as the Banshee, and Maeve Rourke Cassidy. 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 took the infant Theresa with her on a visit to her relatives in Armagh in Northern Ireland. While she was there, Maeve, an innocent bystander, was killed in an IRA (Irish Republican Army) bombing along with a number of other people. No trace of Maeve was found by the authorities and they, and Maeve's relatives who knew of Theresa's existence, assumed that Theresa had also been killed in the explosion and never told Sean that Maeve had had a daughter.[6]

In fact, however, Black Tom Cassidy, her father's cousin and a rival for the love of her mother, had been present at the scene of the explosion and had secretly carried Theresa off with him. Black Tom suspected that Theresa might develop superhuman mutant powers as she grew older, and therefore he intended to raise her secretly so that he might exploit her powers himself. Sean was so filled with anguish when he returned and learned of Maeve's death that he left his ancestral home of Cassidy Keep and threw himself into a series of highly dangerous missions, eventually leading to his resignation from Interpol and his later involvement with the mutant villain team Factor Three.[6]


Theresa's sonic powers emerged at puberty and, a few years later, Black Tom began coercing her aid in committing crimes, whom she called "uncle" out of respect. 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.[7]

There, employing the name Siryn, Theresa battled the original Spider-Woman 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 and Sean were joyfully united at Professor Charles Xavier's mansion. Theresa went to live with her father, who had since retired back at Cassidy Keep and, due to his new girlfriend Dr. Moira MacTaggart, divided their time between Cassidy Keep and Muir Island.[8]

Fallen Angels

Sometime afterward, Theresa lived for a while at the Muir Island Mutant Research Center, owned by Dr. MacTaggert. There Theresa met, and developed a romantic relationship with, Jamie Madrox the Multiple Man. After being informed that the New Mutant Sunspot had runaway, Theresa and Madrox helped to track down the young mutant. Traveling to New York, Theresa and Jamie found Sunspot and Warlock, attempting to rob a church for food, and Gomi, propositioned Bobby da Costa to join the Fallen Angels. Vanisher appeared to further persuade the children and, while still considering, Chance and Ariel appeared and challenged Sunspot to take a chance. Then Bobby, Warlock, and the duplicate Madroxes left with the group.[9]

After tracking the youths, Theresa and the original Madrox, met Boom-Boom and were teleported to the Valley of the Flame, on Dinosaur World, where they were joined by Moon Boy and Devil Dinosaur. After Devil Dinosaur, accidentally, crushed Don the lobster, Gomi's words of not leaving friends after an accident or tragedy struck a cord and Bobby began to second-guess his decision. After all of the mutant's powers, temporarily, went out-of-whack, due to Chance, Ariel suggested that they all leave and teleported them to the Coconut Grove, her home planet. The inhabitants of the Coconut Grove and the leader, Unipar captured the Fallen Angels, intending to use them as experiments to continue their evolution, but the Angels worked together to defeat them and return home. Sunspot and Warlock decided to return to the New Mutants, but Siryn and Madrox chose to remain with the Angels instead of going home to Muir Island.[10]

Muir Island

Siryn eventually returned to Muir Island, only to get caught up in the Shadow King's telepathic influence.[11] When the X-Men came to Muir to investigate, Siryn ended up fighting her own father Banshee, and took advantage of his feelings to beat him for the Shadow King.[12] She was freed from Farouk's influence with the other residents after the Shadow King was defeated on the physical and astral planes.[13]


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.[9] 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.[9]

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.[6]

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.[14]

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.[15]


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.[16]

X-Factor Investigations

Siryn became a member of X-Factor Investigations. She was in a state of denial regarding her father's recent demise, correctly noting that many X-Men had been believed dead only to later return alive. Due to these recent traumas, Siryn was under considerable emotional strain.[17]

She was beaten by Damian Tryp Jr. and captured Doctor Leery. Rictor rescued her, killing Leery in the process. One night, Madrox got drunk; Jamie Prime and a dupe he described as his libido incarnate slept with Siryn and Monet. Jamie was not sure which of them slept with the dupe. Regardless, Jamie kept it going with the both of them, afraid of revealing that he was double-timing them. After a confrontation with Singularity Investigations the members of X-Factor met with Doc Samson, who encouraged Jamie to confess the truth to Monet and Siryn. They did not take it well.[18]

Baby Sean

Theresa discovered that she was pregnant with Madrox's child. After Mutant Town was destroyed by Arcade, X-Factor moved to Detroit. Eventually, she gave birth to a baby boy that she named Sean. Upon picking up Sean, Madrox absorbed him: he had been a dupe all along.[19]

Breaking Points

Terry became the new Morrigan to help save the sanity of Polaris.[20]


X-Factor Vol 3 5 Textless


Banshee is a second generation mutant and possesses sonic acoustic powers similar to those of her father:

Audiokinesis: The 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: She 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: She 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: She can amplify sound carrier waves allowing her to hear conversations or noises from far off.
  • Sonic Shield: She can tighten sound waves around herself or others near her, making a barrier against outside attack.
  • Vocal Disorientation: The ability to change someone’s balance, by affecting their equilibrium using her sonic scream.
  • Vocal Trance: The ability to subtly influence peoples subconscious mind by changing the tones and vibrations of her voice using sonics, the effects tend towards blatant hypnosis. At times she's been even capable of calming down an enraged Hulk (when his rage is not so intense).
  • Vocal Unconsciousness: The 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.


  • Her vocal cords are susceptible to injury from excessive strain in using sonic powers. She has also survived major injuries to her throat at the cost of her sonic powers temporarily. Excessive vocal cord strain can also cause her to temporarily lose her powers.[4]
  • A recovering alcoholic.[6]

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