Increases the armor of the Hero by 3 when worn.
Arthas and Muradin Bronzebeard find one in Frostmourne, chapter 9 of the Warcraft III human campaign, The Scourge of Lordaeron.
Arthas and Kel'Thuzad can also find one in Blackrock n' Roll Too!, chapter 6 of the undead campaign, Path of the Damned.
Grom Hellscream finds one in The Hunter of Shadows, chapter 5 of the orc campaign, The Invasion of Kalimdor.
Illidan can find one in A Destiny of Flame and Sorrow, chapter 6 of the night elf campaign, Eternity's End.
Malfurion, Tyrande, and Maiev can find one in Balancing the Scales, chapter 5 of the Frozen Throne sentinels campaign, Terror of the Tides.
Tyrande and Maiev can find one in Shards of the Alliance, chapter 6 of that campaign.