The Temple of Trithereon lies in the River Quarter of the City of Greyhawk, attended by only a very small clergy. As the deity of Individuality and Retribution, Trithereon's followers only visit the shrine on holy days unless they have retired from the active pursuit of the god's goals, which is to say, adventuring.
The primary active member of Trithereon's clergy in Greyhawk is the war-priestGerald (Ftr3/Clr9), who has recently led several expeditions against gnolls and humans serving the god Hextor in the Cairn Hills.
Gerald has been helped in this enterprise by followers of Heironeous, in what has been an unusual collaboration, as followers of the two religions are generally not on the best of terms due to Chaos vs. Law problems. Primarily amongst those helping Gerald of Trithereon has been Gillian the White (Pal7), a consecrated warrior from the County of Ulek.
The Church of Hextor, in addition to trying to establish a presence in the Cairn Hills, also has major links to the slave trade. Because two of the primary tenets of the Hextorian religion are Might Makes Right and The Loser Is Weak, survivors of any battle are collected by followers of Hextor and shipped to lands that permit slavery. As the Flanaess has been wracked by minor or major wars for the past few centuries, the availablity of slaves has never been an issue.
The route from the Nyr Dyv to the southern seas is thus quite important, and only the Selintan River gives that sort of access. As a result, the City of Greyhawk as the major port on the Selintan River has an agent of the Slavers of Hextor working in it. Master Raeldis (Ftr5/Clr5) seems to make his living as a minor weaponsmith in the Artisan's Quarter, but in reality is the main agent for the priesthood of Hextor. As yet, none of the churches of Good have discovered his secret.
A major construction in the Cairn Hills is currently underway - a Temple of Hextor being built beneath one of the ancient tombs that give the Hills their name. Supervising this work is H'drek (gnoll Ftr2/Clr5). The temple is out of the way of the normal trade routes, but a few lone travellers have disappeared recently in the area.
It should come as no surprise to anyone that the God of Wealth is extremely popular in the merchant-city of Greyhawk, and possesses not only a main temple in the Garden Quarter, but also several smaller shrines attended by lesser priests (Clr2-4) around the city.
Services on Godsday are well attended, though it is unsure of how devout most merchants are. The need to get any advantage they can over their competitors keeps them coming to the temple - and making donations.
As a result, the Church of Zilchus is the wealthiest and most influential in the city. The great masses held on each of the four festivals (Richfest, Brewfest, etc.) are extremely popular, and are invitation only - the invitations coming by the donation of a sizable amount of money to the coffers of the Church. These four services are the one time you can see all of the Oligarchs of the city together, as they all make it a point to attend. (It it possible, nay, even likely, that some send look-alikes rather than attending themselves, but all give the appearance of attending.) The Patriarch of Zilchus has often been a member of the Oligarchs himself; this is certainly the case at the moment with Stakaster Villaine (Clr10) (Note: In a 3E campaign, giving Stakaster a level of 14+ may be appropriate.)
The church provides a constant source of employment for men-at-arms and lower-level adventurers, as merchants often need a military escort through some of the more lawless areas surrounding the Free City. Adventurers most often deal with Father Eras (Clr6), who provides details of current commissions.
It might seem that the church would keep a permanent force of men-at-arms available and patrolling the immediate area to keep down bandits. However the Captain of the Guard (a follower of Heironeous) has kept such reponsibility firmly in the hands of the City. Whilst two or three of the merchant-princes on the Oligarchy might grumble, they do at least see the sense of such a move - keeping the powers of Church and State separated.
On occasion, the church sponsors an expedition into the ruins of Castle Greyhawk or one of the tombs in the Cairn Hills in search of treasure. The temple takes 50% of any treasure found, but provides healing and resurrection (if needed) to the adventurers free of charge.
Zilchus' congregation is made up primarily of those in positions of power and the merchants of the city; the common folk tend to worship Norebo, Pelor and St Cuthbert.
Heironeous has an even lesser shrine in the City than Trithereon, normally tended only by a pair of acolytes. This is mainly due to the disapproval of the Council of Oligarchs - those worthies feeling very uneasy about the followers of any god of war being permitted in the City. They have only been prevented from banning such shrines altogether by the support of their Captain of the Guard (a follower of Heironeous).
THE KNIGHTS ERRANT OF HEIRONEOUS
During the height of the Great Kingdom's power, the churches of the brother-gods Heironeous and Hextor continually strived for ascendancy. One must not assume that because a god is aligned with evil that normal people will automatically condemn them and their followers - War was considered a nasty business, and if the followers of Heironeous were more high-minded about the entire business, well, the followers of Hextor were more effective in battle against the Great Kingdom's enemies.
In any case, once the House of Naelix rose to power (about 437 CY), the favour of the Emperors of the Malachite Throne turned decidedly towards the Church of Hextor and the darker Oeridian deities. The Church of Heironeous found itself losing significant support from the populace, and finally was forced from Rauxes altogether, the Church of Hextor taking over the Cathedral of Heironeous.
The survivors of the purge - for such it was - scattered to lands still uninfected by the taint that had overcome the House of Naelix. A certain group of them chose to remain wanderers, and fight evil as they could and as their abilities allowed. So began the order of the Knights Errant of Heironeous.
The Knights Errant are not an organisation as such, but more of a loosely bound group of like-minded paladins that wander the Flanaess. Their only allegiance is to Heironeous, though some still retain feelings for their homelands and prefer to protect those areas than wander more widely.
The Order is quite refreshing in one aspect: they tend to be more intelligent than most servants of Heironeous. This means that they will avoid a battle they don't think they can win. Though by no means cowards, they do prefer to act with common sense foremost in their minds. This is not to say that a Knight would not sacrifice himself for the cause of good, just that they don't do it with the monotonous regularity that the other Orders tend to display.
There is no leader of the Knights Errant. Individual masters travel alone, or equally commonly, with a young squire they are training in the Knight's Code. The Order has grown away from its origins, and no retaking of the Great Kingdom en masse is foreseeable in the near future, though individual knights occasionally wander into that area on missions of Weal.
The Knights Errant rarely take any permanent home until they feel they have grown too old for the fight. At that point, they renounce all trappings of their old status, and live simply - though most still give aid to those they consider worthy of it.
The Knights Errant are most common in the western half of the Flanaess, but can be found elsewhere. Of their number, Gillian the White (LG human female Pal7) has recently gained fame for several expeditions against slavers and followers of Hextor on the Wild Coast.