His family and ancestors are the tombkeepers of "The Nameless Pharaoh" (Atem). Marik's hatred of the Nameless Pharaoh compels him to disregard his duties as a tombkeeper and turn to a life of evil, eventually developing a split personality as a child. Unbeknownst to Marik, his split personality Yami Marik killed his father.
He wanted to control all 3 Egyptian God Cards (Osiris the Sky Dragon, Obelisk The Tormentor, and The Winged Dragon of Ra) in order to "gain the powers of the Pharaoh" and set his family free of their burden. However, at the end of the saga, he realizes the error of his ways and apologizes for his reckless actions, in turn ridding himself of his split personality. Fulfilling his duty as tombkeeper, Marik returned to Egypt with his sister Ishizu Ishtar and adopted brother Rishid Ishtar to start a new life. The three of them later assisted Yugi and the Pharaoh in Season 5.