Cain

Cain in the Bible
Cain and Abel, according to the Bible, were the first two sons of Adam and Eve (Cain being the eldest). According to the Bible, Abel had pleased God with his sacrificial offering while Cain had not. Because of that, he envied Abel, and so he killed him. God had discovered what happened, so He punished him. But instead of taking his life, He made Cain wander the earth forever, by himself and without ever making human contact. The Bible then states a cursed mark was placed upon Cain, known as the "Mark of Cain". How long ago these events occurred is unknown, though if the Bible is to be believed, he and Abel were the sons of Adam and Eve, placing the event of Abel's murder a generation after Adam and Eve.

Cain in Assassins Creed II
In Assassins Creed though, Cain's story is different. Instead of Cain killing Abel because God was pleased with Abel and not Cain, Cain actually killed Abel to steal his Piece of Eden. The mark Cain was given for killing Abel was then used to create the Templars and collect more Pieces of Eden. Subject 16 also references quotes from the Church of Jesus Christ of Latter Day Saints' "Pearl of Great Price" scripture. The semi hidden message "Templar texts adapted by Mr. Smith" written in Morse code in a glyph sequence, implying that the Mormon or LDS version of Cain and Abel is more accurate, or at the very least, an accurate reflection of the Templars version of events. The relatively unique title of "Master Mahan" is mentioned as the title Cain gave himself for being the master of the great secret. The term "Mahan" is of uncertain meaning, and it does not seem to occur in other versions of the story.