Cain was the firstborn of Adam and Eve, both human hybrids of the First Civilization. At one point in his life, Cain killed his younger brother, Abel, in order to steal the Apple of Eden in his possession. Cain is considered to be the first murderer in recorded human history, while Abel was the first recorded murder victim. Cain's mark, which he was branded with as punishment for killing Abel, became the symbol of the Children of Cain, the organization that would go on to be known centuries later as the Templar Order; a cross under which they united to collect more Pieces of Eden.
Clay Kaczmarek spoke of Cain in one of the Glyphs that he hid within the Animus data. He mentioned Cain's murder of Abel through quotes from the "Pearl of Great Price" scripture of the The Church of Jesus Christ of Latter-day Saints.
- The Templar pirate Jing Lang mentioned the story of Cain and Abel while talking to Vance Travers about the assassination of his brother, Upton Travers.