A sacred talisman and source of power
The Ember functions as a Talisman to all Ember Keepers sworn to its defense. Should the Ember be extinguished, the Keepers lose their magical powers. Furthermore, the loss of an Ember virtually guarantees the abandonment of its stronghold. Naught but total immersion in water can extinguish a sacred Ember.
An ember taken from the forge of Dumathoin himself, every Dwarf stronghold is built around a hearth containing one of these sacred flames. The hearths are tended by the Ember Keepers, the matriarchal clerical order of Dwarven society, who are in turn protected (in theory) by the Hearth Guards.