X Men Movies Canon Wiki


Theresa Cassidy / Siryn is a mutant who can emit a high-pitch sonic scream and daughter of Sean Cassidy / Banshee. She is also a student at Xavier's School For Gifted Youngsters and one of the youngest students during the time.          

Young Syrin in 2001


Early Life[]

Theresa Rourke Cassidy was born in Manhattan in 1986 to Maeve Cassidy, a woman of Irish descendency and Sean Cassidy, one of the founding members of The X Men.

At the age of 13 in 1999, Therry discovered her powers in the same fashion way his father did, as she also kept her abilities a secret ( despite her father being a mutant and revealing his abilities to Therry since she was a small child).

After learning of her abilities, Therry was convinced to become a student at Xavier's institute where she would become part of the "young crew" including Artie Maddicks, Flea, Mondo and Jones

The X-Mansion[]

After arriving, Siryn became aware of her status and even though she was one of the youngest students to train in The Danger Room, she would use her powers in more of a paranoid manner ( much to her teammates' earaches).

She would most likely remain in the classroom as she got along well with Jonothon Starsmore ( Chamber) and her spirit was broken when she found out about his departure from the school. 

The Hidden Agenda ( X2: United)[]

Siryn joined her class and teachers to a museum exhibit which was cancelled due to Pyro's behaviour as well as The X Men's new mission of capturing the mysterious mutant assassin.

Later when the school was invaded by HYDRA, Syrin was rescued at time by Colossus as she was targeted with a tranquilizer and was about to be kidnapped. Peter grabbed her as she was unconscious as he left the institute by a secret exit in the near woods with the other students.

After the incident at Alkali Lake and Jean's death, Therry recovered and returned to her class much to The Professor's appreciation as the students didn't let the recent events mark them.

Aftermath & New Mutants Training Squad[]

Therry would remain just a student even for the following year as she attended all her classes. She would participate at The Professor's funeral where she cried and broke in sorrow as well as being one of the few students who remained at the institute, as she was inspired by Jubilee at that time. It is unknown if Therry became an X Man and began training in The Danger Room after the 'battle for the cure'. She also became proficient enough that she joined Wolverine's squadron.

Relationships, abilities & trivia[]

  1. Sean Cassidy / Banshee - Father.
  2. Jonothon Starsmore / Chamber - Friend and possible teacher during his stay.


  • Sonic scream