The son of Harold Kaczmarek and his wife, Clay was destined, in his father’s eyes, to follow in the family footsteps and become an engineer. From an early age, Clay showed signs of desiring more for himself; at one point saying to his father that he wanted to become an astronaut. As he became older, Clay’s interests began to differ greatly from his father’s hopes, causing a rift between the two.

At some point prior to 2007, Clay succeeded in gaining entrance to a college on an engineering degree, though his father was disappointed that it was not at one of the top-tier institutions. Dejected, Clay secretly began to visit a psychiatrist to discuss his feelings.

Around this time, Clay was approached by William Miles, a member of the Assassin Order, and was offered an induction into the Brotherhood, which he passed, without the knowledge of his father. Following this, Clay’s psychiatrist noticed a marked improvement in his attitude, behavior and outlook, though he was oblivious as to the reasons why.

From that point on, Clay maintained limited contact with his father – whose business was suffering due to the economic downturn in early 2010 – occasionally sending checks to help support the family. His father’s over-dependency soon drove both Clay and his mother away, leaving Harold on his own.

Clay Kaczmarek had a rich and varied ancestry, which quickly caught the attention of Abstergo Industries. Whilst his immediate ancestors lived relatively normal lives, with many on his father’s side of the family taking jobs in engineering, Clay was most notably a direct descendant of Adam; one of the first humans, alongside Eve, who rose in rebellion against the First Civilization.

As Adam was a child of both a human and a member of the First Civilization, Clay had a notable concentration of First Civilization genes in his blood. Clay also had ancestors in ancient Africa, in the Roman forum and in the Far East. Of particular interest to Abstergo was his relation to the Italian House of Auditore, founded by Domenico Auditore in the early 14th century.

His Auditore bloodline ended with Ezio Auditore da Firenze, as Clay’s next ancestor was an illegitimate child. One of his ancestors was also connected with an unknown Queen Isabella, another with Jean de La Fontaine, whilst another participated in the Battle of Gettysburg during the United States Civil War.

For weeks, Clay planned his suicide down to the most minute detail, biding his time and preparing his message, all the while enduring the repeated attempts by Vidic to uncover the location of the Apple of Eden. Eventually, Clay managed to create an artificial construct of himself inside the Animus, through hacking the machine during the night, and split it into thirty pieces to be united by his successor, as well as sending one final e-mail to his father.

The next day, Clay killed himself by slitting his wrists with a ball-point pen and draining his blood out of his body, in order to paint several cryptic messages in the rooms where he was being kept, hoping to ensure his successor recovered the message that he had died to pass on. After his death, Abstergo dumped his body in the Tiber river in Rome. Not long after, Desmond Miles was abducted by Abstergo and forced into the Animus project. In time, he and Lucy escaped from Abstergo, finding their way to an Assassin hideout nearby, wherein he would begin his own explorations of Ezio Auditore’s memories.

During these investigations, the Assassins learned how Clay had managed to hack Abstergo’s Animus before his death, and that in doing so, he had placed twenty glyphs throughout the Animus system, which were subsequently rendered in the visual memories. These encrypted files, which had been saved onto the Abstergo Animus’ memory core that Lucy had stolen, were later unknowingly transferred to Rebecca Crane’s Animus 2.0. After decrypting all twenty files, the Assassins were rewarded with a genetic memory marked “date classified BCE”.

The video showed two freerunners, primordial Adam and Eve, climbing a large glass structure with an Apple of Eden in hand. Following their escape from the hideout, Desmond, Lucy, Rebecca and Shaun Hastings retreated to the last Assassin safe-house in Italy, the Villa Auditore in Monteriggioni. While there, during their exploration of some of Ezio’s later memories, it was discovered that Clay had left ten more glyphs, which corresponded with locations in Renaissance Rome. Upon visiting these indicated landmarks, Desmond discovered several rifts in the Animus programming.

Within each, Desmond solved a cluster puzzle, which then unlocked a piece of a file. Upon compiling them, they revealed a distorted video with the message “the miracle is in the execution”, suggesting that, unlike the video hidden in the Glyphs, the Rifts instead concealed an executable file. Upon accessing it, Desmond found himself in an unknown area within the Animus, and was able to run through a long virtual maze, similar to those within the Animus Virtual Training Program.

At the end of the maze, he found a wire-frame model of Clay, partially broken and made of computing code. Clay told Desmond that all hope was lost, and that he needed to go to Eden to find a woman named Eve. Before vanishing, Clay told Desmond to find him in the darkness.