[@Aristo] On paper it's beholden to the crown, but in reality it's actually mostly upheld through contributions (in raw number of soldiers and financially) made by the Driskard family. It gives them a great deal of political leverage. 

It certainly isn't technically secular. Divination and Constitution mages and priests are a fundamental part of the ranks (especially for the purposes of purification, healing, etc.) Though it's not required to practice the Ten Divines Faith, Minerva is the Patron Goddess for much of Vicelles and prayer to Minerva is common at Fort Stag.