Fire is the physical creation that is the domain of Asha Vahista, in which the Amesha Spenta of “Best Truth” is immanent. Fire is grandly conceived as a force informing all the other [Amesha Spentas], giving them warmth and the spark of life.
In the texts of Zoroaster, it is stated that speaking against the truth and violating the sanctity of promise is detected by the consumption of “water, blazing, of golden color, having the power to detect guilt.”
This analogy of truth that burns and detecting truth through fire is already attested in the very earliest texts. Ahura Vairya dispenses justice through radiance of His fire and the strength of aša. Fire “detects” sinners “by hand-grasping” . An individual who has passed the fiery test (garmo-varah, ordeal by heat), has attained physical and spiritual strength, wisdom, truth and love with serenity.
Because of this association of fire as an auxilliary of truth and justice, the institutions of law and order are established around the everburning Sacred Flame. Acolytes, servants and templars of the Sacred Flame inhabit the cloisters of the fortress-temple, worshipping as well as conducting the will of the flame.
The templars deal with domestic law enforcement as well as working together with the citizenship, militia, and the bloodlines to ensure scurity and protection of Avesta against marauding monsters and the attentions of other antagonists.
When charged with an offence, accused have the option of standing trial in the presence of judges, each a cleric of the Sacred Flame. The alternative is to prove their innocence by stepping through the Sacred Flame, which immolates all but the most pure of souls. Due to the non-specifity of the flame’s judgement, this right has not been evoked from an accused in decades. The only survivor of the flame is the Executor of the Sacred Flame, Ignis.
Street view of the Cathedral of the Sacred Flame