Agrik was originally known as a tribal patron god strongly linked to volcanoes (and to fire in general), and his position as True Lord of everything was revealed to humans through the prophet Ilpylen (see the Agrik article in Gods of Hârn). The new faith included most of the "old" gods of the Azeri people as obedient servants to Agrik, organized in a vast hierarchy; several of the most popular gods of neighbouring tribes were conveniently revealed to in fact be other aspects of Agrik; the True Lord has many alternate names (names are for humans to use; the True Lord doesn't need a name to know himself).
While Agrik has always had a strong "war god" aspect, it is only one facet of a being that according to official dogma is far too vast for humans to completely know. Agrikanism has always accommodated war, but it used to be less warlike than it is today; its present attitude is to some extent a result of centuries of strife during which Agrikans feel they were repeatedly betrayed by foreigners and infidels. The situation has become further polarized after the Azeryan Empire lost its outlying provinces some two centuries ago; most Agrikans feel this would not have happened if they had been fully in charge of the Empire. Currently, the bulk of Agrikanism is governed from the great temple at Lysara, which is also capital of the theocratic Lysara province within the Empire. Agrikans dominate the southern part of Azeryan totally, and are very influential in the northwest, but weaker in the northeast, where cosmopolitan traditions (and a Morgathian ruling class) keeps them from taking over (attempts at taking over were a major contribution to the Empire's near-collapse in the sixth century). Outside the Empire, there exist many splinter sects whose doctrine and practice often deviates significantly from orthodoxy; many of these have effectively been out of touch since about 500 TR or even earlier. Hârnic Agrikans are quite clearly an example of this. Heresy and factionalism has often plagued the metropolitan Church as well, but there it has always happened that one faction (in each case the orthodox one, since they get to write the historical records) actually won those power struggles and purged the Church of the heretics (many of the splinter sects, of course, descend from heretics fleeing a purge).
At the beginning, utter chaos reigned, but then the Lord Agrik coalesced as the first and only true god. Born of fire, he burned away much of the chaos to create some space to do works of order in, and he drew forth many lesser spirits to do his bidding in the great work of creation, making them into demigods as his servants, and taking some of them as his wives (for some were of female aspect). But some of the lesser spirits did not obey the True Lord, and they ran away to hide in the darkness near the edge of chaos, and they planted seeds of corruption in Agrik's creation, for they were jealous of it. In his wisdom, Agrik let them do this, because it would give his later creations (us) something to struggle against so we could prove our worth.
Agrik's demigods who stayed obedient, however, did him proud in helping to form the world -- mountains, oceans, rivers were all shaped from the bones of the Earth which Agrik had melted with his power, and later they fashioned living things to fill the Earth and to draw nourishment from the fire Agrik placed in the sky, and at the end they made humans and Agrik put some of his fire into their souls so they would have true spirit and ambition. Agrik and his demigods then left the humans alone for a long time, so as to let them multiply and fill the earth, and to see what they would do with themselves.
But the demons hiding in the darkness had prepared themselves also, one of them had made himself leader and taken power over the rest, and his true name is not to be spoken, but we call him Naveh when we must talk of him, or the Dark One, or many other call-names. Naveh had been the last of Lord Agrik's demigods to renounce the True Lord during the early stages of creation, after he had been spurned by one of the True Lord's wives whom he had coveted. Naveh was more powerful than any of the other demons to begin with, since he had been bathed in the True Lord's glorious light for much longer than they had, and he later learned how to draw forth more power from the chaos at the edge of things, enough power to become a real threat to the world of mortals -- and sometimes even to corrupt other demigods as well.
The first act of the Dark One was to slowly cloud the memories of humans, so that over the years, many people forgot about the True Lord altogether, and even those who remembered him did so imperfectly. Then he sent many false dreams of other gods, so that people would worship false religions, and much confusion reigned. But then the Lord Agrik sent us a prophet to remind us of the truth, and ever since Ilpylen's day we have known our true place.
Unfortunately, most people in the world have still not accepted the dominion of the True Lord. Their minds have been poisoned by the lies of the Dark One, and they have been blinded by the false glory of illusory gods. This is particularly bad among those who are not of the Azeri; it seems that the longer a people has lived under a lie, the harder it is to get them to see truth, and Ilpylen was chosen from that tribe which had remembered Agrik's truth best. Now, most of the world is under the shadow of the Dark One, and even in our own ranks there are hidden traitors, who bear the corruption of Naveh in their hearts. It is for this reason that we must be doubly vigilant, and ever ready to burn out corruption wherever it may be found, so that the world may return to Agrik's order. If we fail, then ultimately the True Lord may choose to wipe Kethira clean with fire and begin Creation again; foreign infidels are great liars when they say that our Lord is merciless, for it is only out of mercy that he has not already done so.
In our places of power, we govern as Agrik intended, and our people enjoy peace and prosperity under our law. While there is no glory greater than serving Agrik as a priest or a soldier, there is some measure of glory to be had in doing anything well; excellence in any field of endeavor pleases the Maker. If farming is your profession, you can win a place for yourself in the afterlife by being a good farmer and by obeying those who have been set above you, according to the law. Every profession has its designated patron among the demigods, and prayers and offerings may be directed to Agrik via these delegates (a practice which the Triadic heretics have copied, except they instead pray to "saints" who are supposedly humans who have been elevated to demidivine status after their deaths, or so they claim).
Sadly, not even our own Church itself is entirely proof against corruption. Throughout our history, the Church has often been troubled by heresies, both in the form of outright infiltration by the forces of darkness, and in the form of previously true believers turning to wrong ideas. The wiles of the Dark One are many, and we must be ever watchful against his influence, for he will do anything to bring us down. Enemies within our own ranks are even worse than those without, and must be purged with no mercy; they deserve whatever punishment can be devised, and then some. Trust no one, and keep your mace handy.
Their warriors are admirably brave and skilled, and are worthy opponents, although they are burdened with strange notions of honor, which give them a bit of a weak point -- if they follow them, hypocrites that they are. We must never forget that they are tools of the Dark One, but we must also remember that they are for the most part unwitting tools; it is not unheard of that a Triadist may be made to see the True Light. Opinions have been divided through the years on how to best defeat Triadism; the currently favored strategy at Lysara is to avoid direct armed confrontation for at least a generation or two, while instead directing our efforts at strengthening our position within the Empire by political means, and strengthening our position in the greater world by regaining the Imperial provinces around the Venarian Sea (thus also strengthening the position of our true faith in those areas). A direct confrontation at this time would lead to disaster for the True Faith, and is just what the Dark One wants to see; this is true, for many of his secret followers within our own ranks confessed to it when they were put to the question during the latest purges.
Those who worship Morgath are basically of two types: There are those who began to worship him while he was still Agrik's servant, in the mistaken belief (born of ignorance) that Morgath was the true god, and who do not acknowledge Morgath's fall into chaotic insanity. These are no worse than any other infidels, and can sometimes be converted to the true faith by force of persuasion rather than by force of arms. Then there are those whose traditions are more recent, and who share fully in the chaotic insanity; these should be put out of their misery as soon as possible. I have heard that there is even a place where those lunatics are the rulers, I think it is a city somewhere on Hârn -- if any place ever needed burning, that is it.
There are some people, though, who seem overly fond of Halea's charms, to the point of forgetting who's really calling the shots; these bear watching, since the Dark One may be trying to lead them astray. In foreign lands, there are already places where Halea is worshipped as an independent goddess; this is nothing but foolishness, but it may be dangerous foolishness.