Sean Cassidy is an Irish mutant with the ability to perform a 'sonic scream'. Sean has taken the name Banshee and is currently alligned with the Anglo-Japanese superhero team Excalibur.
Before Excalibur #1Edit
Prior to his first appearance in the All*Star universe, Sean Cassidy had been affiliated with the police force Interpol. While employed by Interpol, Sean fell in love with a young woman called Maeve Rourke. The pair of them were soon engaged to be wed and expecting their first child.
However, unfortunately for Sean his cousin Tom would complicate matters, kidnapping his wife-to-be and blackmailing Sean into aiding him in IRA terrorist actions in Northern Ireland. Tom's plan was intended to see Sean take the fall for the act, but instead saw both cousins arrested and imprisoned by the British government for seventeen years.
Recruitment (Excalibur #1-3)Edit
In the first arc of Excalibur, Sean was released from prison following a quick psychological evaluation from Betsy Braddock on the condition that he signed up with the team.
Having joined Excalibur, Sean learned that although his fiancee Maeve had died shortly after his imprisonment she had first given birth to their daughter, Theresa. Accompanied by his new team mates in Excalibur, Sean promptly departed to Portugal in search of his estranged offspring. On arrival the sarch was complicated by an unlikely meeting with Black Tom, the extra-dimensional superhero team known as the Exiles and a little-known religious cult, whom, it emerged, had coaxed Theresa into joining their ranks. Complicating the matter further was the presence of an alternate version of Theresa among the number of the Exiles. The united pair of superhero teams met hostilities from the cult calling themselves the Spineless Ones and had to figh hard to survive the encounter. When Sean finally met his daughter for the first time he was dismayed to find that his indoctrinated offspring was intent on murdering him. Unable to bring himself to mercilessly fight back against his own daughter, Sean was soon defeated and awaited the killing blow. Theresa would surely have killed Sean had the Exiles' alternate Theresa interrupted at that point, slaying her counterpart.
Sean joined the cast of Excalibur in Excalibur #1 and has appeared with the team in all issues of Excalibur since. Sean has also appeared in all issues of the Excalibur Exiles crossover miniseries.