Theresa Cassidy

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Name: Theresa Maeve Rourke Cassidy
Occupation: Superhero; detective; student (X-Men Movieverse)
Title/Rank: Siryn, Banshee, Morrigan
Sonique (AU!AOA)
Status: alive
Relationships: Sean Cassidy (Banshee, father), Maeve Rourke-Cassidy (mother),
Tom Cassidy (Black Tom, father’s cousin), Victoria Donnely (mother’s cousin),
Jamie Madrox (love interest), Nate Grey (AU!AOA love interest), Sean (son[1])
Fandom: Marvel Comics, X-Men, X-Force, X-Men Movieverse
Other: Wikipedia
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Theresa Cassidy is the alter ego of Siryn from the Marvel Comics series The X-Men.


Theresa possesses the mutant ability of a "sonic scream" and the power of flight like her father Banshee. Theresa first appeared in Spider-Woman #37 (April 1981).

Shauna Kain portrays her in the X-Men Movieverse.


This article or section needs expansion.


Theresa's popular het ship is with Wade Wilson (Deadpool). She has also been shipped with Jamie Maddox (Multiple Man) and James Proudstar (Warpath). She is rarely shipped with Scott Summers (Cyclops).

Although femslash pairings are more rare, Theresa is usually paired up with Monet St. Croix (M) or Felicia Hardy (Black Cat).


Examples Wanted: Editors are encouraged to add more examples or a wider variety of examples.



X-men Comics:

X-Men Movieverse:

Fan Casting fanart:



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Links and Resources


  1. X-Factor (vol. 3) #39. When Theresa gave birth to baby Sean and Jamie Madrox was given him to hold, he instantly (against Jamie's Will) reabsorbed the baby - revealing that the baby was an infant dupe.