|Sean was born into an Irish mafia family, the eldest of two sons. His mother died delivering Sean's younger brother Joseph when Sean was nine and thus the raising of the two boys was left to Rory and a succession of nannys.
His mother's death affected Sean profoundly; suffering intense emotional distress, and it was this event which first triggered his mutant psionic powers, though due to their subtle and invisible nature it would not be discovered for some years even by Sean himself. The only thing observably different about him was that somehow, no matter what sort of rough scrape he got in, he always came through unscathed.
Rory was a man of influence in the Irish mob and over the years as he watched his boys grow up he saw in Sean much of himself and had decided early on that when Sean was old enough he would begin to groom the lad to follow in his footsteps, but Joseph would be kept from the dark end of the family business. Then events which would have taken their natural course came to an abrupt head when Sean was 13 yrs old and Rory was out on buisiness. Sean and Joseph were home alone and the boys found one of their dad's guns while playing hide and seek. Being boys they started playing with it, and Joseph accidentally fired the gun while it was pointed at Sean. Tragedy was averted however as Sean's therefore unrevealed powers prevented him from taking any damage at all...the bullet itself merely flattened seemingly at the surface of his skin and thus the boys discovered that an invisible force field protected Sean.
They were good boys and not prone to hiding things from their father and thus they immediately told their dad as soon as he returned from his "business trip'...ie "hit"...what had happened. Though he didn't believe the boys at first, the fact of the matter was easily proved. Once he got over the shock Rory was just as surprised as the boys were. Not knowing exactly how this was possible and not really caring Rory made the boys swear to never ever tell another soul about Sean's newfound power.
However as the years passed he worked with Sean to discover every thing he could do with this new found ability and to push its limits. When Sean turned 16 Rory began taking him along on jobs and Rory soon saw in Sean a potential to rise in the ranks of the mafia, live a better life, and give Joseph the chance to go to college and really make something of himself. Sean was also quickly accepted and fondly regarded by many of his father's associates. Early on the other made men and friends of the family called Sean the "Rookie", as his boyish appearance and inexperience were evident; even as he gained more experience the name stayed with him though it eventually got shortened to just the "Rook".
As predicted by his father Sean "Rookie" Sullivan quickly skyrocketed through the rank and file of the mob and became an elite "trouble-shooter" and all around go-to guy for inflicting violence. Of course his abilities couldn't be kept a secret forever and soon it was well known among the underworld of New York that Rook Sullivan was invulnerable and unstoppable; few heavy hitters were as feared as he was. Sean and Rory both were content with this; as Sean's rep grew both their lots improved. Sean was respected by his peers and the upper echelons of the extended New York mafia families, and feared by rivals and enemies.
When Sean turned 27 Joseph was 18 and had just graduated from high school. Kept apart from his brother and father's work, he was a good student and had excellent prospects. He was accepted to Harvard, perhaps thanks to a little string pulling but at least partially due to merit, and Rory threw a big party for his "college boy". Life could not have been better for the Sullivans. However not everyone was happy for the family's successes; one of Sean's enemies named Vincent Tolintine decided that this party was the perfect place to catch Sean unawares and settle up an old score for good. Vinnie and a few of his "friends" hit the party fast and hard, and in the ensuing blood bath Rory and Joseph were both fatally shot along with several other close friends and relatives.
Fighting off the attack singlehandedly, Sean took stock and realized his family had been slain. Pushed beyond his ability to deal with such a tragedy Sean snapped and entered into a murderous rage. He hunted down Vincent and those that had assisted him. Leaving a trail of bodies behind him he worked his way through the Tolentine organization until he discovered that Vinnie had holed up in an abandoned warehouse with as many gunmen as he could call in. Rook went directly there and killed every person in the building in a bloodbath the press later called the Tolintine Massacre. Almost fourty men were brutally killed in that warehouse, but the police were unable to attain any forensic evidence of the perpetrators. Of course people knew who did it; but no body was going to put the finger on a man capable of such a thing.
Sean wasn't satisfied however. He wanted to destroy all those even vaguely associated with the Tolintines, and wipe the entire family out. In the aftermath the higher ups in his own mafia family warned Sean that his determination to get vengeance was going to start a war with many other powerful families and they tried to get Sean to agree that vendetta had been met by killing Vinnie and his men, but Sean would have none of it. He wanted all those responsible dead and he wouldn't settle for anything less. Sean failed to heed the warnings of his superiors and killed several more people in the Tolentine organization. Sean was soon approached by his Don and told him that an accord had been made with the other families and Rook was no longer welcome in the family or the neighborhood. Out of respect for the Sullivans years of loyalty to the family (and the fact that they couldn't really do much to Rook without calling in some powered help), the Don indicated that Sean would be allowed to live and go in peace, and could stay until after the funeral services for his family.
Rory and Joseph's funerals were held soon after; while Sean stood there watching the caskets be lowered into the ground and listening to the priest's benediction Sean questioned why God would take his brother and leave him to live. Sean never believed he or his old man were going to go heaven but his baby brother was a different story all together; if ever there was someone who should have lived a long and happy life it was Joseph. Sean needed answers to these questions and so after the funeral he confronted the priest with them. Father O'Malley did his best to console Sean and tried to explain the will of God. He talked of how the wages of sin must be paid before one can leave the mortal coil and that perhaps God had need of Sean and his gift.
When Sean asked Father O'Malley if everyone was capable of redemption the Father merely smiled and said "As long as you are truly penitent when asking for forgiveness my son, and always do your best and care for your fellow man, then God's mercy and love knows no bounds". The Father struck a cord inside Sean, and from that moment on he was changed man. As Sean turned to leave Father O'Malley gave Sean one last piece of advice in following God's will... "Do unto others my son as thou wouldst have them do unto you". Sean smiled as he looked the Father in the eye and said "I always have Father". The next day Sean said what few good byes he had to make and left town.
He soon arrived in Millennium City to begin a new life and unsure of what to do next he looked up a friend of Father O'Malley's named Father Mulcahey. Sean took to the gruff but wise priest right away, and Father Mulcahey soon became the keeper of his conscience and the guiding hand to the path of Sean's redemption. He aided him in practical matters as well, helping Sean find a place to live in Dearborne near the parish and a job at a HOME DEPOT store. Sean has no idea how he is supposed to redeem himself in the eyes of God, but when he asks Father Mulcahey about it the Father only says that Sean will have to work that out with God on his own one day at a time.
Following his instincts and trying to find ways to earn his salvation, Sean protects those who can't protect themselves, helps out those in danger whenever, however, and wherever he can. He started off with simple things like freeing some people trapped in a wrecked car, rescuing a handful of people from a burning apartment, and scaring off loitering drug dealers and thugs from the neighboorhood, and doing other good deeds as the need arose. Sean didn't consider these to be acts of heroism, just what anyone would do in his place if they were able. The other people in his neighborhood saw it differently and soon Sean noticed he was getting a different kind of respect from the grateful citizens that recognized him.
He soon found himself spending his free time patrolling the neighborhood looking for trouble, stopping a number of break-ins, breaking up a prostituition ring, and making it unsafe for street criminals to play their trade in his area. Sean knew he couldn't stop all crime or clean up the city completely but he saw it as his duty to do what he could. And thus it wasn't long before his neighboorhood patrolling led him to become involved in stopping supercrime, eventual membership as one of the first members of the supergroup known as the Millennial Men, and even government approval as a sanctioned superhero. He has become a well known and well respected superhero with a loyal fan base and the support of many.
In addition to fighting such dangerous and well known supervillains as Holocaust, Black Harlequinn, and Talisman, Rook has also been on several "missionary" trips to Africa and South America via the church, where he has in truth gone out to assist fellow mutants being interred in IHA run mutant camps in third world countries. Rook has thus far kept the true nature of these trips a secret from his fellow Mill Men, seeing it as a personal crusade, but perhaps one day he will call on the bonds of friendship and team loyalty he has earned with his contributions to his fellow teammates to assist him in his war on the genocidal mutant hating organization.