Theresa Cassidy is a mutant who can emit a high-pitch sonic scream. She is a student at Xavier's School for Gifted Youngsters.

During William Stryker's attack on the mansion, her scream alerted the rest of the school that they were under attack. She was captured, but was rescued by Colossus.[1]


She can scream very loudly, and at a high-pitch.

Strength level

Normal human female of her age.

Shauna Kain portrays Theresa in X2 and X-Men: The Last Stand.

  • While Siryn is traditionally Banshee's daughter, X-Men: Days of Future Past establishes, that Banshee passed away prior to 1973. This makes it unlikely that he's her father, as she was a teenager, in the early 21th century.

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