This article contains lore taken from Warcraft III: Reign of Chaos, Warcraft III: The Frozen Throne, the manuals, and/or official bonus maps.
- Tome of Intelligence +2
- "Permanently increases Intelligence."
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 sentinels campaign, Terror of the Tides.
Malfurion, Tyrande and Maiev can find one in 
[50-70] Balancing the Scales, chapter 5 of that campaign.
Malfurion and Maiev can also find one in The Ruins of Dalaran, chapter 7 of that campaign.