Robe of Vecna

Robe of Vecna is robe for wizards and it offers like all the robes of the aligned Archmagi, a basic armor class of 5. But the robe of Vecna can be used by all aligned, offers magical resistance of 10%, instead of 5% and lowers the amount of time needed to cast spell by 4 units, but it doesn't offer a +1 bonus to all saving throws, which the Robes of the Aligned Archmagi do. This item appears in Baldur's Gate II: Shadows of Amn and Baldur's Gate II: Enhanced Edition.

In-game description
"Robe of Vecna This robe doesn't even have close to the power that the two famous artifacts, the Hand and Eye of Vecna possess. Still, from simply being worn by the powerful lich, the robe absorbed enough magical energies to become a potent magic item."