Sean Cassidy is a mutant with the ability to create powerful sonic waves with his voice. In 1962 he was recruited by Charles Xavier and Erik Lensherr in order for him to join their team of mutant peacekeepers they were forming for the CIA.

After the Hellfire Club tried to recuit them, Sean and the others relocated to Xavier's mansion where they began training to defeat Shaw. Xavier taught him how to control his ability and use it to fly by using a harness developed by Hank McCoy.

During the Cuban Missile Crisis, when the team assembled to finally confront the Hellfire Club, faced Angel alongside Havok.[1]

Some time later but prior to 1973 he was killed, likely as part of Bolivar Trask's experiments on mutants.[2]

Years late, Sean's name appeared on a list of names Mystique scrolled through on William Stryker's computer while searching for Magneto's file.[3]


Sean Cassidy (Earth-10005) from X-Men First Class (film) 0004.jpg

Sound Manipulation: Cassidy possessed the mutant ability to control sound with his vocal chords. He typically manifested the power by screaming, but he's also capable of achieving various effects:

  • Sonic Scream: ability to shatter solid objects with a sonic scream
  • Flight: ability to fly at subsonic speeds by using his voice to propel him through the air and ride the sound waves.
  • Sonar: can use his sonic powers as a form of sonar (Sound Navigation and Ranging). By sending out a precise, pure note and listening to the returning, altered wavefront of the note, he can evaluate his surroundings in total darkness with varying degrees of resolution.
  • Vocal Disorientation: ability to change someone’s balance, by affecting their equilibrium using his sonic scream
  • Sound Immunity: Banshee's hearing and equilibrium are unaffected by his power or other similar abilities.

Superhuman Vocal Stamina: possesses superhuman stamina in his lungs, throat, and vocal cords.


  • Banshee's Wings: Professor X developed a harness for Banshee's X-Uniform. Using the Harness and his sonic scream he is able to glide on air current. Using the harness he is able to fly at subsonic speeds.

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