Siryn of X-Force (Marvel Comics) (Cassidy) by Liefeld, sigh


Power Level:
Game system: DC Heroes Role-Playing Game


Siryn first appeared in 1981, teaming with Black Tom Cassidy and Juggernaut against Spider-Woman.

She becomes a major character in 1991 when she joins Cable’s X-Force.

This profile covers her X-Force years, until she loses her power to Feral’s slash at her throat.


  • Real Name: Theresa Rourke Cassidy.
  • Marital Status: Single.
  • Known Relatives: Thomas “Black Tom” Cassidy (“uncle”, in fact her father’s cousin), Sean Cassidy aka Banshee (father), Maeve Rourke Cassidy (mother, deceased).
  • Group Affiliation: Black Tom Cassidy, Fallen Angels, X-Force.
  • Base of Operations: Mobile.
  • Height: 5’7″ Weight: 130 lbs.
  • Eyes: Blue Hair: Red


Powers & Abilities

Siryn is the mutant daughter of Banshee. She has inherited her father’s sonic powers.

Under Black Tom’s tutelage, she developed some stunts of her own. During the few years she spent on Muir Island, Moira continued her training.

History (part 1)

Theresa Rourke Cassidy is the mutant daughter of Sean Cassidy, the mutant who was not yet known as Banshee, and Maeve Rourke Cassidy.


Birth and infancy in Black Tom’s custody

Soon after his marriage, Sean Cassidy, an Interpol agent, was sent on an undercover anti-terrorists mission for months. When he left his wife, he didn’t know she was pregnant. Shortly after Theresa’s birth, Maeve took the infant with her on a visit to relatives in Armagh in Northern Ireland. There, they were caught in an IRA (Irish Republican Army) bombing.

The authorities found no trace of Maeve nor Theresa. Maeve’s relatives who knew of Theresa’s birth assumed she also died in the bombing. Nobody knew that Thomas “Black Tom” Cassidy, Sean’s cousin and his rival for both the heart of Maeve and the family’s heirloom, had taken Theresa in his custody.


When he came back from his mission, Sean learned of Maeve’s death and was crushed by grief. Nobody told him of his daughter’s birth and presumed death. But Black Tom was there. He was ready to talk to him about Theresa. However, Sean went mad.

He blamed Tom for not taking enough care of his wife during his absence. He attacked him and broke his leg. And that’s how Black Tom developed a limp. Needless to say, it muted Black Tom’s willingness to reveal his secret.

Siryn of X-Force (Marvel Comics) (Cassidy) screaming at a forest

Black Tom was already involved in criminal activities, in partnership with Juggernaut. He suspected that Theresa might develop superhuman mutant powers as she grew older. Therefore he intended to raise her, officially as his, so that he might exploit her powers for himself.

Until she proved useful to him, he sent her to St. Elizabeth Boarding School (we can assume it to be a Roman Catholic Private School, with its lot of religious strictures). Resenting her “uncle” for sending her away, she started to drink alcohol. What started as a way of getting back at her uncle soon became an addiction.

Teenage years

Theresa’s sonic powers emerged at puberty. Soon, Black Tom attracted her in his criminal career as jewels’ thief. She was attracted by the thrill, and booze eased her bad conscience.

Eventually, Theresa accompanied Black Tom and Juggernaut to San Francisco. There, employing the name Siryn, Theresa battled the original Spider-Woman and several of the X-Men. It ended in Black Tom’s temporary capture.

While in custody, Black Tom gentlemanly exonerated Theresa of responsibility for his crimes. He also wrote to Sean to explain who she was.

Theresa and Sean joyfully united at Professor Charles Xavier’s mansion. She went to live with her father, who had since retired back at Cassidy Keep. With her father in a relationship with Dr. Moira MacTaggart, Theresa divided her time between Cassidy Keep and Muir Island.


We couldn’t resist since it’s a mostly-Irish song about siren-like seduction. Here I’ve picked a recent-as-of-this-writing cover version, by Asta (lead vocals), Cosmo’s Midnight (bass, keyboards/drums) and session musicians.

It is a fairly direct, but quite good and fun, cover of the Moloko song as remixed by Boris Dlugosch 20 years before. The harmonies between Asta and the back-up singers even directly reference Róisín Murphy’s distinctive voice.
– Ed.

The brilliant 1999 original is available for download on Amazon .

History (part 2)

Fallen Angels

(See the New Mutants team profile #2 for further details on this era.)

At this time, Siryn was in a romantic relationship with The Multiple Man. They accompanied Moira McTaggart to New York when Magneto called for help. Magneto and Moira dispatched Theresa and Jamie to bring back the missing Sunspot and Warlock. They got drafted in Ariel’s plans to bring mutants to Coconut Grove.

One of Madrox’s duplicate took his independence and was left over, and a bit forgotten, in New York. Even Madrox can’t keep track of all his dupes, if they wander too far from his main self.

After these adventures, they decided to stay with the Fallen Angels. A bit older than them, they expected to provide them with better guidance than what the Vanisher offered. Siryn stayed with them for an untold period of time before going back to her father in Cassidy Keep and Muir Island.

Once back on the islands, she routed a pitiful attempt of the Irish government to build an Irish super-heroes team.

Kings of Pain and The Muir Island Saga

She fell for The Shadow King’s evil influence just like the other inhabitants of Muir Island. Everybody’s more violent sides were exacerbated.

Siryn of X-Force (Marvel Comics) (Cassidy) early appearance vs. Spider-Woman

During the “Kings of Pain” cross-over, Moira ordered Siryn and her fellow islanders to repel The New Warriors who were boarding the island. It took Cable and his New Mutants (soon to become X-Force), to cool Moira’s spirit. Though Siryn was there during the final confrontation with the reborn Proteus, she didn’t take an important part in the battle.

When Xavier and the X-Men assaulted Muir to defeat The Shadow King, Siryn, still under evil influence, battled her father and beat him. She tricked him in lowering his guard before his daughter. But Iceman took her down during the final battle.

Her relationship with Multiple Man came to an end. It’s not clear how. It was strongly hinted, later, that Madrox’s dupe left over in New York had something to do with it. The “dupe” might have been the true Jamie in love with Siryn, while the one who came back to Muir was not. When wandering too far, too long, from his main, Madrox’s dupes became independent.

Madrox ended up in the USA, where Val Cooper reorganized X-Factor as a government sponsored team. This came after the failure of previous government super-team the Freedom Force.

Meet The X-Force

Black Tom Cassidy allied with Arianna Jankos, owner of a high-tech company. From the top of the World Trade Center, Jankos had gathered some of the wealthiest men in the country. These were the heads of companies trying to buy out her company. Among these gentlemen were Roberto DaCosta and his financial mentor Gideon.

Black Tom kidnapped and ransomed all of them, thus preventing Jankos from losing her company. To repay him, she provided the way to bring back Juggernaut from his banishment in another dimension. The former duo reunited, Black Tom and Juggernaut carried on with the hostages situation.

Siryn of X-Force (Marvel Comics) (Cassidy) charging with Proudstar

Learning her uncle was back on the terrorism trail, Siryn tried to stop him. Juggernaut welcomed her. He and Black Tom sent her flying away quicker than she expected. That’s when Cable arrived with his X-Force. Theresa teamed with them. With the help of Spider-Man, they neutralized Juggernaut.

Cable severely wounded Black Tom, who fell in an elevator shaft. He was discreetly rescued by Deadpool. Deadpool also teleported Juggernaut away from the lost battle.

With Madrox gone from her life, and lots of bad memories of Proteus and the Shadow King waiting for her in Muir, Theresa accepted Cable’s offer to stay with X-Force.

X-Cutioner’s song

Cable left X-Force to mind his own business with Tolliver, Deadpool and the real Domino. He left Cannonball in charge.

During one of her concerts, Lila Cheyney gave Professor X the opportunity to address a public speech of fraternity between humans and mutants. However, this created an opportunity for Stryfe to strike.

Stryfe was a perfect evil clone of Cable. Stryfe posed as Cable to critically shoot Professor X in public. This threw a monkey’s wrench in the relationship between the youngsters of X-Force and the other X-Teams.

Cannonball and X-Force stood by their absent founder. They faced The X-Men and X-Factor who wanted to get Cable. Theresa’s reunion with Jamie ended in his team putting hers behind bars. Or rather, force fielded holding cell in the X-Mansion’s Danger Room.

During the arrest and the detention afterward, there was a lot of patronizing from the elders over how Cable had messed up with the youngsters perceptions of Xavier’s dream. Madrox had a chance to explain that the one in love with her was the dupe killed in New York. The one currently in charge now wasn’t in love with her.

Siryn of X-Force (Marvel Comics) (Cassidy) sonic strafing run

Anyway, Siryn spent all of this story arc in detention in the Danger Room.

When the matter was finally settled, and while Cannonball was making his statement to Xavier, Siryn and Warpath stole data from Xavier’s computer. Xavier tried to persuade her to leave X-Force and join The X-Men. She kindly refused. She preferred to stay with people who, like her, were left angry after traumatic experiences.

X-Force’s status as a rogue mutants troop would prove useful to Professor X in the future.


She was but a minor member of X-Force. Siryn was easily taken down, kidnapped and use as bait… As eldest of the team, she put a lot of pressure on herself to do well on the battlefield. With a drinking problem to start with, it didn’t help. She started to get drunk a lot.

Warpath tried to cover for her. It didn’t fool Cable.

Warpath had developed a crush on her. But it was unrequited love.

Siryn of X-Force (Marvel Comics) (Cassidy) drinking beers

She wanted to take some time to think straight again and asked James to come with her to Cassidy Keep. There, his friendship proved to be stronger than his love for her. He pushed her to confront the ghosts of her childhood. Her love was forever lost to him, but she kicked her addiction. Not that this will prevent him from trying to woo her again.


Theresa kept in touch with her father. She was working with him to track Black Tom, when they ran into Deadpool. While Banshee left to do his own inquiry, Siryn teamed with Wilson to follow up the lead of Black Tom’s troops.

Siryn started to take interest in Deadpool, half fascinated by him, half pitying him. He gave her a special way to get in touch with him, which would prove useful. He became quite obsessive about her: dreaming about her, stalking her, spying on her, at night, through the window, while she was sleeping.

Siryn of X-Force (Marvel Comics) (Cassidy) sleeping

Occasionally, they had adventures together. She had a good influence on him, making him act more seriously and start to get credits as a human being. She was not ready to get romantically involved with him, but she made it an incentive for him to get along a path of redemption.

Leading X-Force

After the universe recovered from The Age of Apocalypse, the tension between X-Men and X-Force cooled down. Everybody was welcome to the X-Mansion again. Xavier even provided X-Force with new uniforms. Siryn abandoned her traditional green and yellow colors.

Cannonball made it to graduation which, in X-teams’ language, means integrating into The X-Men. As she was the oldest of the X-Force, Cable appointed Theresa field leader, while he was taking a step back from them.

She had to deal with her team being mind controlled to attack Cable, Boomer’s change to Meltdown after the Sabertooth incident, Proudstar making out with Risque, Shatterstar possibly not originating from Mojoworld… She managed some feats too, like infiltrating SHIELD’s Helicarrier to free Cyclops, or exposing the Gamemaster’s mind games at the Weisman institute to free Deadpool.

Siryn of X-Force (Marvel Comics) (Cassidy) punching Deadpool, which is good

During the Onslaught event, Xavier’s deep spirit maintained Siryn out of Onslaught’s grip. She thus managed to extract her teammates from his influence. During Operation: Zero Tolerance, she had to take hard field decisions, like leaving Domino (and the MLF) behind to evacuate the rest of her team.

She also led her team in covert operations, with SHIELD unofficial blessing, to free fellow mutants held prisoners by Bastion and his Alpha Sentinels.

Low profile

After Zero Tolerance, when Cable asked X-Force to take new identities and go into hiding, she stressed her teammates’ decision to decline. Cable’s training was enough to handle anything. They didn’t need to run away. Instead, she led them to a quiet errand throughout the USA. Rictor left to take care of his family in Mexico, and Shatterstar went with him.

Siryn of X-Force (Marvel Comics) (Cassidy) flying casually on her back

Still much caring for Proudstar, she helped him further investigate his tribe’s massacre. When they found the truth, James died confronting the perpetrators of the massacre. Siryn called for the help of Moonstar’s mystical experience as a death angel. While Dani was in the spirit world with Bobby and Tabitha, Theresa stood as the anchor to the physical world.

X-Force then settled in San Fransisco, in a warehouse provided by DaCosta International.


Eventually, Cannonball got tired of being patronized by his fellow X-Men. Taking the excuse of a visit to his family in Kentucky, he left the grown-ups’ team. Soon he got involved in trouble which reunited him with X-Force. Leadership might have been an issue, but Sam was a too much of a team player to engage in a cockfight.

Siryn of X-Force (Marvel Comics) (Cassidy) slashed by Feral

They confronted King Bedlam and his New Hellions. X-Force faced failures from their past.

  • Tarot, who died with the other Hellions at the hand of Fitzroy, had somehow been resuscitated.
  • Magma, former member of Sam, Roberto and Dani’s New Mutants was now rejecting their common history and living solely for herself, associating with Bedlam for money.
  • Paradigm was the result of some kind of experiment with something like Warlock’s trans-mode virus.
  • And Feral, whom X-Force sent to The Vault for the murder of her mother, and now infected by the Legacy Virus, was in a nihilistic streak to take down as many people as she could in her fall.

Siryn only shared a common history with Feral. As expected, she wanted to deal with her. Unfortunately, Feral landed a devastating slash on Siryn’s throat, missing the jugular but not the vocal chords. Theresa may never be able to utter a sound again.

Theresa took very badly to being powerless. She shut all her friends out, nearly relapsed in alcoholism, thought about suicide. After a few days, she quietly left to live with a distant aunt in North California.


She’s a bit of an Irish teenage girl’s cliché : flaming locks of long red hair, Irish skin and eyes of emerald, mmm, blue actually.

Siryn of X-Force (Marvel Comics) (Cassidy) gardening face closeup

Her first costume was yellow and green with extra striped fabric between arms and legs to increase the lift of her flying power (like a wingsuit used for BASE-jumping). It was purposefully very similar to Banshee’s original costume.

She used similar costumes afterward, with very little variations and always with the original green and yellow. When X-Force received uniforms from Xavier, she had a dark blue body glove with a yellow short vest (with wingsuit sleeves) and thigh high yellow boots.


Theresa is an easy going young woman. She’s earnest and reliable.

She’s a very good team player and a very dedicated leader. She actually thoroughly studied super-heroes tactics to be up to the task. After she took leadership, when Cable or Domino were moving with her team, she never doubted their legitimacy to take over.

Siryn of X-Force (Marvel Comics) (Cassidy) dream tram with Banshee and Deadpool

When it comes to relationships, it’s another matter. While in a rather steady environment in Muir, she had a stable one with Madrox. While on the edge with X-Force, she was scared of getting too close, except maybe with people she won’t be seeing often. That’s how she pushed Proudstar away but was not so blunt with Deadpool. She’s certainly not an easy target.

Deep inside, she resents the lack of parental love. The Shadow King’s possession was a milestone in her life. It shaped her decision to join X-Force.

She has a tendency to self-loathing that surfaces when she’s drunk. Before hooking with X-Force, alcohol was her way of filling these voids. After Proudstar’s intervention, it was her teammates and her responsibility as their leader.



“You needn’t be formal with me, sir. Most people find ‘Siryn’ an easier name to remember than ‘Theresa Cassidy’.”

Cable: “Well, darlin’, if you’re in the mood to kick the crud out of something, then you’ve hooked up with the right crew.”
Siryn: “Just point the way.”

Siryn: “Domino… It worked ! I have his helmet !”
Juggernaut: “Hey ! Theresa ! Get back here with that thing !”

Siryn: “Jamie, after all we shared, don’t make me fight ye !”
Multiple 1: “Siryn…”
Multiple 2: “…Not to be rude…”
Multiple 3: “…But what exactly have we shared…”
Multiple 4: “…Besides your sonic scream triggering my duplicates ?”

“I was just admirin’ the colors… looks a lot like Ireland come autumn, y’know.”

“Muir Island became a dead place. And I felt dead inside, as well, Professor. As dead as the grave […] I wanted to be with people who were like me… People who were dead inside, as well. People too wounded… too angry t’be with anyone else. That’s why I went with Cable an’ his lot.”

“You can’t like someone who hates themselves AS MUCH AS I HATE M’SELF!”

Siryn: “Hey ! HEY ! You want t’keep that new hand, then get it off me… NOW ! I’m warnin’ ye to check y’r libido at the door, mercboy.”
Deadpool: “I see. Playing hard to get.”
Siryn: “Try impossible.”

(X-Force playing gridiron football)
Shatterstar: “Will Theresa be joining us ?”
Siryn: “Maybe if’n ye choose t’play real football.”

Cannonball: “Thanks Jimmy [Proudstar]. Didn’t see you walk in, but where Siryn goes, Warpath is soon to follow, huh ?”

Game Stats — DC Heroes RPG

Tell me more about the game stats

Siryn (X-Force era)

Dex: 04 Str: 02 Bod: 04 Motivation: Responsibility of Power
Int: 04 Wil: 04 Min: 04 Occupation: Adventuress
Inf: 04 Aur: 03 Spi: 04 Wealth: 004
Init: 011 HP: 040

Sonic Blast: 12, Flash [sonic]: 08, Flight: 07, Force Shield: 05, Hypnotism: 06, Mental Freeze: 05, Sleep: 05, Super Ventriloquism: 05, Vibe: 08

Bonuses and Limitations:

  • Power Loss [Sonic Blast is neutralized if she can’t make sounds: like gagged] (-2).
  • All power are Contingent on Sonic Blast [the above Power Loss neutralizes all other powers](-1).
  • Hypnotism, Mental Freeze and Sleep requires hearing, thus are blocked by Shade [sonic] (-2).
  • Flash, Mental Freeze and Sleep has area effect (+1).
  • Mental Freeze and Sleep are Minor Marginal (-1).

Artist (Actor): 04*, Vehicles (Land): 02

Leadership, Rich Family (Banshee and Cassidy Keep).

Black Tom Cassidy (Low), Banshee (High), Deadpool (High), Moira McTaggart (Low).

MIA toward alcohol, Mistrust (Mutant), Mistrust (X-Force).

They tried to make me go to rehab

Before Warpath’s intervention on her alcoholism, she had SIA (Alcohol) instead of MIA.

Early Siryn

When she first appears, young and teaming with her foster “uncle” Black Tom Cassidy, she’s not so battle hardened and experienced (even though it is said she has a good mastery of her powers). Here are her stats during this period:

Dex: 03 Str: 02 Bod: 03 Motivation: Thrill of Adventure
Int: 03 Wil: 02 Min: 03 Occupation: Part time criminal/Schoolgirl
Inf: 03 Aur: 02 Spi: 04 Wealth: 002
Init: 009 HP: 020

Sonic Blast: 10, Flash [sonic]: 07, Flight: 07, Force Shield: 05, Hypnotism: 06, Super Ventriloquism: 05, Vibe: 08

Bonuses and Limitations:

  • Power Loss [Sonic Blast is neutralized if she can’t make sounds: like gagged] (-2).
  • All power are Contingent on Sonic Blast [the above Power Loss neutralizes all other powers](-1).
  • Flash has area effect (+1).
  • Hypnotism requires hearing, thus is blocked by Shade [sonic] (-2).

None at this stage.

Rich Friend (Black Tom Cassidy).

Black Tom Cassidy (High), Juggernaut (Low).

Age (young), Innocent, SIA (Alcohol), Mistrust (Allied to recognized criminals), Mistrust (Mutant).

Design notes

  • Banshee’s writeup introduces Flash [sonic]. I assume there could be a Shade [sonic] and it defends against any sound based manipulative powers.
  • Wingsuit Costume: Somehow, her flight power is enhanced by the use of a costume designed as a BASE-jump wingsuit. If a neat-picking GM wants to model this, use the following adjustments:
    • Bonuses and Limitations: Flight has Power Loss (-2 AP without the help of some kind of gliding equipment).
    • Equipment: WINGSUIT [Bod: 05, Misc. Adv.: Neutralizes Flight Power Loss].

By Nicolas Lemaçon.

Source of Character: Marvel Comics (1st appearance in Spider-Woman #37 in 1981, then Fallen Angels in 1987, then X-Force in 1991).

Helper(s): Sébastien Andrivet, Darci.

Writeup completed on the 27th of May, 2017.