The Rangers are an elite group of covert operatives who operate as part of the Alliance military. Officially, they are members of the First File and answerable only to the Pendragon; unofficially, they operate as the intelligence branch of the Alliance.
While the organization has many customs and practices, these are largely demonstrations and tests of loyalty. The Rangers are in no way religous and many of the more public faces of the group are clearly just there for the pay check. The Rangers are not a fighting force; their task is to watch and listen.
The Rangers started as messengers and spies working for Eieber and his army. With backing from the Cardinal Clerics, Eieber began to model his intelligence force on the Templars, specifically copying the organizational structure that allowed them to be fast and agile, yet made the organization essentially impossible to bring down.
Following the end of the Mage Wars, Eieber had little need for military spies, and instead fashioned his Rangers into the eyes and ears of his new Order of Slayer Dragons. With the Rangers leading the way, Eieber always knew where to send his best people to stop the Mage Wars from ever happening again.