This article contains lore taken from Warcraft III: Reign of Chaos, Warcraft III: The Frozen Throne, the manuals, and/or official bonus maps.
Permanently increases Intelligence.
Source
Maiev can find one in Rise of the Naga, and one in The Tomb of Sargeras, chapter 1 and 3 of the Frozen Throne night elf campaign, Terror of the Tides.