Sean grew up in County Mayo, Ireland alongside his cousin Tom. The two were as close as brothers. However, Sean's life lead him to a career in law enforcement and investigation, while Tom's lead to law breaking an all-around shadyness. The two competed for the love of a woman by the name of Maeve Rourke, and Sean won out in the end, and the two were married.
Maeve died in a terrorist attack while visiting family in Northern Ireland, but not before giving birth to Sean's daughter, Theresa. At the time, Sean was deep undercover. When he returned home and learned of his wife's death, he lashed out at Tom, blaming him for not protecting her. Tom had yet to tell Sean about his baby girl, and decided he never would, as revenge, after Sean attacked him and left him with a permenant limp.
Sean continued his work with Interpol, and met the X-Men and Charles Xavier during an incident involving the criminal organization Factor Three. Later, Sean moved to the US and became an officer of the NYPD.
When the X-Men were indisposed, Charles Xavier contacted him for help with a mission, and he soon joined the team full-time. Since then, he has frequently had a spot on the X-Men's team roster, but even more often, served as a teacher and mentor for Xavier's students.
He met his daughter when she was nearly an adult, after Black Tom sent her to him with a letter explaining what he had done. He has since attempted to make up for the years he was absent in her life, but it hasn't been an easy undertaking for either of them.
He is currently a teacher at Xavier's School For Gifted Youngsters and an X-Man, though he does make a lot of jokes about "being too old for this ****" in regards to the latter.
While Sean's vocal chords are physically built to generate superhuman levels of sound, what really makes his powers particularly useful to him is his psionic ability to manipulate any sound he creates with them, making him able to control the frequency and volume, as well as even focus the effects to certain areas. He can use this to achieve simple things such as "throwing" his voice to much more impressive feats such as using shifting frequencies and vibrations to affect the equilibrium of an opponent to induce anything from mild dizzyness, nausea, headaches, or even unconciousness.
Sean is a veteran X-Man with years of experience, not only as a superhero, but as an agent of Interpol and officer of the NYPD. He trains regularly and is capable of teaching others to defend themselves (and has, in fact, given instruction to many younger X-Men).
Perception:Enhanced Hearing (5)
Sean's hearing is well within the "superhuman" hearing range, able to detect sounds no normal person could detect. Students attempting to sneak out of their dorm rooms /curse/ this one.
Banshee can utilize his scream to propel himself through the air, travelling on psionically-controlled soundwaves at subsonic speeds. He is able to carry one person with him, provided they are not too heavy for him to physically lift in his arms. It's worth noting he cannot talk while flying, as well.
He can play the bad cop, and can be pretty darn scary when he does. Through the use of intimidation or more suble means such as lies and manipulation, he can usually coax information from the average criminal.
Sean has trained with and is capable of using small firearms, but it has been a few years since he has used one regularly.
Sean is able to send out inaudible (to most humans, anyway) sonic frequencies and get a mental picture of his surroundings by listening to how they bounce off of things.
Toughness:Sonic Immunity (10)
There is simply no way to harm Sean using a sonic attack, regardless of volume or frequency. /Annoying/ him, on the other hand, is entirely possible.
Power:Sonic Scream (7)
Not surprising considering his code name, Banshee can unleash a sonic scream so powerful it can shatter most solid matter (provided it is not unusually tough or treated to survive such things). Also, he does not require a microphone, ever.
Toughness:Sonic Shield (4)
Banshee can focus the sound of his sonic scream to create a shield capable of deflecting bullets and other simple ranged weapons. This shield would be large enough to provide cover for about 4-5 average-sized people, standing closely together.
Sean's uniform, while definitely not the most visually impressive of all the X-Men's, has arm-webbing "wings" that allow him to harnass sonic energy in order to fly. The costume is made of unstable molecules, and grants him the same advantages that his team mates' uniforms do (aside from the looking cool thing, his never does that). Grants him a toughness level of 4, masks him from genetic scans and includes a team comm link built into it.
Sean was one /hell/ of an agent when he was with Interpol. He's tracked down criminals and terrorists of varying threat levels and has a pretty hefty pile of folders in his "closed case" files. Augments Perception or Intellect when used.
Sean has perfect pitch, a lovely singing voice and can play piano fairly well. He mostly leans towards jazz and old country music. Great on karaoke nights! Doesn't augment any stats.
Possibly Sean's true passion, he is extremely skilled when it comes to mentoring and instructing students in most basic subjects (and some of the not so basic ones that fledgling X-Men would need to study). He's not just the guy with the book that has the answers filled in, but someone who generally /cares/ about the education of his charges. Some of his methods may be a bit unorthodox, and he can be a little strict at times, but he is very patient. He's also very, very proud of his students. Affects Intellect when used.
Sean would make one heck of an improv actor. He spent months under assumed identities in the course of his work with Interpol, and has also acted as a handler for other agents doing the same. It's been years since he's played that game, but he'd be more than capable of doing it again. Affects Intellect or Perception.
Sean is a high-functioning alcoholic, meaning he is dependant on alcohol, but he is able to function in his daily life and maintain relatively healthy relationships (well, with anyone he's not related to). Were he to quit drinking, he would have a period of withdrawal and would always remain an alcoholic, albeit one in recovery. He is aware that his drinking can be a problem, but is not quite ready to admit that he is /addicted/ to the drink. He is also aware that his drinking makes him a walking stereotype. It helps that his tolerance is very, very high and it's increadibly rare for him to get falling-down drunk. But in times of extreme stress or grief, the bottle does become the proverbial crutch.
Theresa Cassidy, aka Siryn, is Sean's biological daughter, though he did not raise her. The fact that he wasn't aware of her existence until she was nearly an adult is his greatest regret. He tries to maintain ties with her, but being truly close is difficult for the both of them. He would also do /anything/ for her, and putting her in danger is a sure way to manipulate him.
Both a flaw and something of a boon at times, Sean and his cousin are completely unable to affect each other directly with their powers. They can, however, affect the enviroment around each other in combat. When Sean broke Tom's leg, it was by making the ground underneath him dissolve.
Sean is a hero, through and through. And will jump in to spare another person harm, even at the cost of his own well-being, or even his life. When he dies, it will likely not be from old age or illness. This is an easily exploitable flaw for those willing to put lives at risk to get to Banshee.
Okay, so technically Black Tom is his cousin. But growing up, they may well have been brothers. His issues with Thomas Cassidy are many, and the two meeting will almost always end in physical violence. Worse, he still actually /cares/ for him in the way only family can, which makes the fights all the more emotionally taxing.
If Sean pushes his powers too far (say, saving the nation of Japan from Moses Magnum), he loses all his vocal-based powers for anywhere from a few days to months, and possibly permenantly depending on how far he has pushed himself.
Injure his throat or otherwise render him unable to create sound, and one takes out the majority of Banshee's effectiveness in the field.