From the introduction:
The Shattered Shield of Arnisant is all that remains of the artifact known as the Shield of Aroden. The origins of the shield itself are shrouded in mystery—some believe that the god Aroden carried it when he was a mortal, while others claim that it was fashioned by Aroden after his apotheosis and gifted to his first priest. Known for certain is that it was carried by the Taldan General Arnisant in the final battle with Tar-Baphon, the Whispering Tyrant, during the Shining Crusade. The general used the power of the shield to great effect during the war, rallying the crusaders, rescuing his troops, and preventing defeats from becoming slaughters. In the climactic battle of that decades-long war, the Whispering Tyrant attempted to transport Arnisant’s still-beating heart into his hand by means of a wish spell. The shield blocked the spell, but the artifact shattered under the power of the lich’s magic. One of the shield’s splinters buried itself in the Whispering Tyrant’s hand, consuming him in holy fire and destroying his mortal form. His spirit then fled to its phylactery deep in the dungeons below Gallowspire.