Dylan grew up in the hostile climate in Britain following Hitler's ascension to power in Germany. When he and his father dug in the earth in order to erect an air shelter, they discovered a sleeping vampire, who attacked them. The vampire killed his father, but Dylan managed to drive a stake into her heart. Shaken to the core, he suffered bad dreams and began to suspect that he had failed to kill the monster.
A campaign of the local Prince to keep the Masquerade was to keep all vampires away from Dylan. In a desperate attempt to understand what had happened, Dylan met Katherine, a diabolist of the Sabbat. Katherine used Dylan's infatuation with her to make him a hunter that would strike at her enemies within the Sabbat. Dylan became a dangerously effective killer under her tutelage and she considered introducing him into the infernal. When she revealed her true nature, however, Dylan drove a stake into her heart and fled. After he had massacred dozens of Kindred during the attacks of the Luftwaffe on London, Queen Anne Bowesley finally contracted an Assamite to bring him down. The Assamite, however, was destroyed during the attack and Dylan's mother found her end in the blitz. Heart-broken, Dylan began to search again for vampires, hoping to get killed by them until he left Britain for France.
It was then that the Sabbat found him and introduced him into their fold, telling him that the Camarilla were at fault for the death of his father. Turning to the Paths of Enlightenment, he reunited with his former mentor Katherine, who introduced him to the Path of Evil Revelations. Keeping his new allegiances secret, Dylan managed to join the Black Hand in 1985, dedicating himself fully to revenge against the Camarilla.
In V20 details of Dylan's biography are slightly different. Born in Scotland, Dylan Bruce was only sixteen years of age when he moved to London to dig trenches and build bomb shelters alongside his father Malcolm in the late 1930s. Dylan was not privy to the details of his father’s business dealings, and was unaware that Malcolm had been hired by a Ventrue lord named Gotsdam who was interested in their family’s heritage and engineering expertise. Gotsdam rightly predicted a second world war was near at hand, and in anticipation the Ventrue paid considerable sums to the Bruce family to build bomb shelters (that were secretly fortified as havens) and defenses in key locations scattered throughout England. When war was finally declared and the draft was imminent, Dylan’s father begged Gotsdam to save his son, unaware of the Kindred’s true nature. Malcolm’s request was not unusual, for everyone had noticed how Gotsdam became increasingly interested in Dylan due to his keen, strategic mind and regal bearing. The Ventrue succumbed to Malcolm’s pleas, and used his considerable connections to arrange for Dylan to join the short-lived British Expeditionary Force (BEF) to fight during the Twilight War. Under an assumed name, Gotsdam himself marched alongside Dylan on the Belgian-French border for a few nights leaving Malcolm to fend for himself in London. Unlike other units in the British Army, the BEF spent their time patrolling the border and building fortifications and shelters as they had in England, during this early phase of World War II. Dylan worked tirelessly at Gotsdam’s direction, unaware he had been building even more havens for the Camarilla for many months, until one fateful night. Dylan and a few other soldiers had been invited to a dance at a farmstead in the area and, like many young men his age, was interested in meeting girls. The one who approached him during the party that night, however, was no girl at all — but another vampire, an infernalist and disavowed member of the Sabbat named Katherine.
Dread Names, Red List mentioned that Katherine's deepest desire — to unleash the demon Drakonsyr that resided within the body of Gotsdam’s ancient sire, Tiamat. Katherine attached herself to Dylan and guided him from the shadows. She uses Dylan as a pawn, to twist his mind before he became Embraced by Gotsdam, so she could create a link to Tiamat through his blood. Though she could have left him near death at their first meeting, some Alastors believe that Katherine’s goal was more complex than petty. After all, if Dylan had been Embraced by Gotsdam before she could influence him, Katherine might never get the chance later on. The book also mentions Dylan listens voice inside his head — the words of Tiamat. Neither Dylan nor the other members of the Sabbat are aware of Katherine’s plans, Tiamat’s influence, or the deep commands Gotsdam implanted into his mind. Dylan himself believes he has not seen Gotsdam since his Embrace, and counts the Ventrue amongst the hated enemies of the Sabbat and fools in general. Ironically, Dylan’s ignorance is the only thing keeping him alive, for while he is being manipulated, he remains unaware of the many forces using him as a pawn in a much longer game.
Beckett's Jyhad Diary as well has some information about Bruce. So, Mary the Black intends to make Constantinople a literal gateway to Hell, recruiting to her side the Carthaginian Assamite Eshmunazar, and reaching out to Dylan Bruce to become the third party. She intends for the ancient Eshmunazar to act as darkness, while she and Michael play the role of balance. Dylan Bruce is to become Lucifer’s light, before plunging the entire city — and possibly the world — into Hell. Also, the book mentioned that Bruce tried to track Sword of Nul, killing anyone who kept it from him, and chewing on their soul awhile. When Beckett excavated Enosch Sarcophagus, Kemintiri, Petaniqua and Bruce have attacked him and incanted some ritual — necromantic, some manner of black thaumaturgy— before opening Sarcophagus.