More information can be found in the Darkest Dungeon article on The Cutting Room Floor wiki. Non-religious heroes can refuse services from the Tavern for the Abbey, and religious heroes can refuse services from the Abbey for the Tavern. Religion is mostly a scrapped mechanic in-game, as only five camping skills utilize the mechanic.The Light is the religion behind the crusades, and is a source of power utilized by the Vestal and the Flagellant. 'Religious' heroes in Darkest Dungeon worship an entity or god known as the 'Light.' This religion is similar to abrahamic religions, as it is seen as a holy entity in-universe.

Prior to The Color Of Madness DLC, the Abomination was unable to be placed in a party with a religious hero.Courageous- Bonus stress reduction, randomly reduces stress of allies. Focused- bonus ACC and randomly boosts ACC of allies. As a result, a Vestal with the Faithless quirk will still prevent nighttime ambushes when using Sanctuary. Virtues: Stalwart- Bonus stress and move resist I think.

Note: Religion is NOT affected by quirks such as Faithless, Flagellant and God-Fearing.

There's no harm in using the Vestal's skills if the party is non-religious, unless better stress healing or PROT skills are available. If its for a trinket is means you have a 15 greater chance of gettting a virtue after a stress check (getting 100 stress). Unless you have good stress healers, try to avoid adding additional stress. In Darkest Dungeon, stress gain should be minimized at all costs and can be the difference between a successful expedition or a much needed retreat.

Darkest dungeon all virtues