The Millennium Eye (
The Millennium Eye was created 3,000 years prior with other Millennium Items by Aknadin. After its creation, Aknadin himself put on the Eye, sacrificing his left eye in the process, either wishing for his son Seto to become pharaoh (which was impossible due to Seto's birth status) in the manga or to ward off Zorc Necrophades in the anime. It was later used to summon Zorc Necrophades.
Later, a faction of the Tomb Keepers guarded the Millennium Eye, along with the Ring, Scale, and Key. One of the members, Shadi, placed the Millennium Eye into Maximillion Pegasus's left eye (in the manga, Pegasus's eye was cut out before the item was forced into the emptied socket). After having it successfully in place of his left eye, Pegasus saw his deceased wife Cecelia Pegasus for a fleeting moment. To be inconspicuous, Pegasus then wore the eye for the rest of his life (normally hidden under his hair). Wanting to bring that image of his wife back, Pegasus used the Millennium Eye's power to read minds during his first Duel with Yami Yugi. After the Duel, Pegasus used the Eye's power to trap Yugi's Grandpa's soul to lure Yugi to Duelist Kingdom.
When Seto Kaiba arrived, Pegasus used his Eye's power to trap Mokuba Kaiba's soul. When Pegasus Dueled Kaiba, he used the Eye's power to read Kaiba's mind and deck. After Pegasus defeated Kaiba, the former used the Eye's power to take the latter's soul. While the Duelist Kingdom's finals occurred, Pegasus used his Eye's power to look into each Duelist's hearts during Yami Yugi's and Mai Valentine's Duel and when Joey Wheeler's and Bandit Keith's Duel. After Mai surrendered to Yami Yugi and Joey defeated Keith, Pegasus used his Eye's power to "punish" Keith with a Penalty Game (this only happened in the manga).
When Pegasus and Yami Yugi Dueled, Pegasus used the Millennium Eye's power to read Yami Yugi's mind and strategies until Yami Yugi and Yugi Muto switched places to confuse Pegasus, laying cards face-down and then allowing the other persona to take control so that Pegasus couldn't read their strategy. This strategy worked, allowing the two Yugis to destroy Pegasus's powerful "Toon World" card, but Pegasus used the Eye's power to turn their Duel into a Shadow Game which eventually incapacitated Yugi's soul as he lacked the strength to keep operating in the Shadow Realm. Just when Pegasus used the Eye's power to read Yugi's mind, Yugi's friends blocked Pegasus' Eye's power and Yugi used this opportunity to defeat Pegasus, restoring the souls of Solomon, Seto Kaiba and Mokuba Kaiba. Unknown to everyone, Pegasus was also defeated by Yami Bakura, who won the Millennium Eye from him in a Shadow Game; in the manga, Dark Bakura simply took the eye from Pegasus after his loss against Dark Yugi, which lead to his death.
Sometime later, Dark Bakura gave the Millennium Eye to Yugi in the manga while Yami Bakura gave it to Kaiba in the anime after their Duel as a lure to get to him travel to where the Pharaoh Atem resided. After the Ceremonial Battle, the Eye, along with the other Millennium Items, were buried underground.
The Millennium Eye appears on the crown of "Ma'at".
The Millennium Eye's primary ability is to peer into the mind of an opponent, which allows the owner to know what they're thinking at all times, no matter what. When Dueling, the owner can use the Eye to see their opponent's cards and strategies clearly, giving them a significant advantage. They can also see their hidden memories and sense if there is a spirit inhabiting their minds.
Like the rest of the Millennium Items, it can also initiate Shadow Games, materialize the effects of Duel Monsters cards, and also cast illusions and protect its owner from harm among other magical powers. It can also initiate the Mind Card Penalty Game, where it seals the soul of someone inside a card, or in the manga, other types of Penalty Game, as Pegasus used a fatal one on Keith for cheating. Other lesser powers include sensing the location of people of interest.
In the manga, it was said that anyone who wears the Eye will be given one wish.
The two known wielders of the the Millennium Eye (Pegasus and Aknadin) share similar traits and stories. Both have lost a loved one that determine their "wish" when they receive the Eye. Also, both are responsible for the form of the Shadow Games take place in their respective time periods due to what they created based on ancient writing and images (Pegasus creating Duel Monsters and Aknadin creating the Millennium Items themselves).