Hood of Cunning

Increases the Agility and Intelligence of the Hero by 4 when worn.

This item is a blood-red hood that fastens about the wearer's neck with a simple silver clasp. The fabric's edges are decorated with a shimmering gilded weave. The hood may not be worn without draping it over the head- if the owner attempts to do so it always flops back into place on its own, as if pushed upwards by a firm but gentle breeze.

Source
Arthas finds one in Fall of Silvermoon, chapter 5 of the Warcraft III undead campaign, Path of the Damned.

Thrall and Cairne Bloodhoof can find one in By Demons Be Driven, chapter 8 of the orc campaign, The Invasion of Kalimdor.

Kael, Lady Vashj and Illidan can find one in Gates of the Abyss, chapter 5 of the Frozen Throne alliance campaign, Curse of the Blood Elves.