They believe that the sinful lives of those of the world below caused the rot and the path to cleansing it lies by removing that sin, both from their lives, from the lives of others and from all forms of record, be they in the skies or within the rot.
The sect has many followers from all walks of life. As such it has varying degrees of religious devotion, these can be categorised into 4 groups: The Grain, The Perfects and the Holy Orders of the Blue and Red Crosses.
From the average follower to the local priest, the grain constitutes the bulk of the Crossed Hearts followers. Due to the harsh reality of life, not all of the churches rules can be followed all of the time and sin must be committed for survival. This is the identifier that they are part of the grain; preservation above sin, life instead of grace. This is not to say they take this decision lightly (although many of the less devout certainly would) it is just that then push comes to shove their life means more to them than their values.
It takes a certain kind of person to be a Perfect: great amounts of self-control, perseverance and religious fanaticism to disregard ones natural instincts and follow ones Holy Book to the letter. Perfects are exactly that, perfect in the eyes of the church. They fulfil the roles of priests in major cities, religious diplomats and theologians on top of spreading the word of the church far and wide.
The Order of the Blue/Red Crossed Heart:
These two religious orders act as the might of the church. Essentially modern Templars these men and women (respectively) are bound to their honour to defend their faith and seek out heretics and the knowledge of the old world and purge them from existence. Due to a somewhat vague section of their Holy Book these orders are not bound to the standards of their religion (although many Perfects believe they should be) and are free to do as they please in the endless crusade to rid the world from sin and the rot below. Although many follow at least some of the churches rules there are some who follow none at all and these are the most dangerous, for lack of consequence can make someone merciless and psychotic.
The church affects the lives of it's followers in many ways. It provides a clear but restrictive set of rules to be followed, many of which seems somewhat archaic to those outside of the religion. It is generally pacifist in nature; prohibiting violence against the other races, except in self-defence, as well as making fish and cows sacred and therefore applicable to the same protections as the humans. Other forms of meats must be "cleansed" with blessed water and salt before cooking.
It also determines the clothes that they can wear: bright colours are barred from all garments except the armour of the militaristic orders. Patterning is similarly prohibited unless it is as a result of the weave of the garment.
Most pertinent is the belief in the purging of Old World knowledge. The church is responsible for much of the loss of knowledge during The Ascension and continues to destroy the tomes of the past. In more recent years the church has been able to make their way into the rot in the quest to purge the lost knowledge that still resides there. Heavy casualties resulted in all missions but all were deemed successful thanks to number of books recovered and destroyed. The most successful of these missions involved the burning of an entire library, giving off such a great heat the rot was temporarily cleansed from the area, however only for a short period.
The church's views make it incompatible with many other religious groups. Their relation with The Magi is tenuous at best, only made stable by the eminent risk of mutual destruction.
The only exception to this is thier alliance with the Technocult whom supply and maintain most of their technolgy, although the cult's faith would be considered heretical thier technical skills are second to none and give the church an edge over most other factions. To prevent a holy war within the church the cult agrees to recognise the Omnissiah as an aspect of the Twelve angels and the Church allows to read and memorise old world books and records (under the guise to searching for secret holy messages) before destroying the. However this compromise does not fully relive tensions and frequent clashes between the two groups happen frequently