Hasan is a mysterious ancient being in the Yu-Gi-Oh! anime and manga and is the messenger of the Egyptian Pharaohs. For centuries he has defended the honor of Egypt's Kings, and he made a vow with Atem's father Aknamkanon to protect his son no matter what.
In Dawn of the Duel, he was Yami Yugi's "master item" during the Dark RPG against Yami Bakura. Hassan appeared before Atem, after he had fallen into a chasm. He advised him to rest, and left. Later, when Aknadin became the Great Shadow Magus, he intercepted one of his attacks and redirected it to Yami Bakura's Hourglass Token that froze time, thus destroying it and making time move again. He later perished at the hands of Zorc Necrophades, protecting the Pharaoh and his guards. Shadi later possessed his body, and died again.
He appeared before Atem when he had fallen into a chasm, and advised him to rest. Later, Bobasa transformed into Hasan, and introduced him as his other self and the spirit of the Millennium Stone. He later flew away to protect Atem at Kul Elna. He protected Atem and his guards from one of Zorc's attacks, and later died from of his later attacks, revealing his face, Shadi.