For most of the existence of mortals there was but one recognized religion among sentient races, the adoration of the Old Gods. Since there was no other religion to contrast it with, this religion never had a name, instead people were simply known as Observers, Believers, and the Faithless.
Since the end of the Great War, Helaim Reverence has become the dominant form of religion. Practiced universally in Arent and widely in Kel’thos it has no holidays or services, but requires the devout to tithe to House d’Thorn and to fast on days of the new moon.
In absence of reverence to the old gods many of the surface races of Kel’thos turned to nature worship, ascribing spirits to natural occurrences and prominent figures, such as the sun, the moon, the sea, the wind, etc…