Akhenaden (アクナディン, Akunadin) was the guardian of the Millennium Eye and the brother of Pharaoh Akunamkanon. During his younger days, he helped orchestrate the massacre at Kul Elna so he could create the Millennium Items to defend his brother's kingdom (the slaughter was kept a secret). To protect his family from anyone seeking revenge, he reluctantly abandoned his wife and his son, Seto. Seto later entered the pharaoh's court as a priest, but Akhenaden kept their relationship a secret. Despite these actions, he is portrayed to be kind, as when he opposed Seto's plan to round up and imprison criminals for their Ka. He is also shown to openly regret his actions at Kul Elna.
When Bakura attacked the kingdom and revealed he had escaped the massacre at Kul Elna, Akhenaden was hunted down and eventually cornered in his sanctuary. Bakura used his newly acquired Millennium Ring to influence Akhenaden's mind, and the priest became convinced Seto should overthrow the pharaoh and take control of the kingdom. He told Seto this, but Seto refused. In preparation for Seto's rise nonetheless, Akhenaden kidnapped a young girl named Kisara, whose spirit contained a powerful White Dragon. Akhenaden later returned the Millennium Items to the Millennium Stone and began Zorc's resurrection. Zorc then used his power to transform Akhenaden into the Great Shadow Magus. Akhenaden continued to try to persuade Seto to rebel and become pharaoh, going as far as to kidnap him so Pharaoh Atem and the other guardians couldn't interfere. But when Kisara convinced Seto to completely turn his back on him and stay with the Pharaoh, Akhenaden went mad. He attacked the pair, sealing Kisara's spirit in stone along with her dragon. Seto, in grief, attempted to stab Akhenaden, only to have to have Akhenaden/Zorc take posession of his body. Kisara's spirit protected Seto, however, and Akhenaden was destroyed.
In the original manga, the battle between Atem and Seto was the one in which Atem sealed his soul into the Millenium Puzzle, along with the soul of Akhenaden, which was possessed by Zorc. In the Memory World Dark RPG, Akhenaden's possessed soul aids Bakura in trying to kill Atem and resurrect the full soul of Zorc, most notably by turning back time when Bakura is defeated, and later animating the memory version of the Great Shadow Magus. Akhenaden's mummy is kept at Bakura's side by the RPG table, and it's skull is split open after Zorc's defeat, showing that Zorc's darkness has vanished completely. Akhenaden's purified soul is later seen in the afterlife as Atem walks through the door to it; his appearance being that of how he looked before he created the Millenium Items.