The relic of Saint Kinga is a large rose quartz that has been cut into the shape of a stylized human heart. The relic is approximately the size of a human heart.
The legend is that Saint Kings himself unearthed the quartz while mining. After his death a finger bone of the Saint was placed inside the rose quartz through a miracle.
The Heart normally resides in Old St. Kinga's Chapel in the Old Mines of Cerro Rico, however when the cataclysm fell upon the mine, the priest of that temple took the relic and attempted to flee with it. He traveled up through the mine attempting to exit via the Old Drift but was killed when Desconocido sent a blast of dragonfire down the tunnel.
Later, Stronin Stonebreaker found the corpse still clutching the relic and retrieved it, taking it it back to Old Stonebreaker Hall where he hid it. The relic is one of the reasons the Stonebreakers have survived so long, it’s power shield whatever chamber it is placed in and prevented the Fear from claiming the dwarf brothers.