One of the difficulties people have in imagining the Yelmalio cult is that the best described temple is the one in Prax, aka Sun County. Sun County, if you all recall was founded in 877 ST by Yelmalio-worshipping mercenaries from the Sun Dome Temple in Dragon Pass. In 1120 ST it was cut off from the rest of the cult with the Dragonkill War until Dorasar founded New Pavis in 1550.
The center of the Yelmalio cult during this time was South Peloria, where some 10 Sun Dome temples maintained their autonomy. Allied with Orlanthi tribes, Sable People from the Hungry Plateau, and elves from Rist, they followed Jannisor to answer the plea of the rebelling Dara Happan Tripolis and waged war on the new Lunar Empire. In 1275 they reached the Inner City of Glamour, when they were betrayed by the Sable People and defeated.
The Sun Dome temples of Saird were part of the Kynnelfing Alliance that fought against Hwarin Dalthippa from 1330-1350. Defeated, the Sun Dome temples were forced to submit to the Conquering Daughter – those that did not fled to Dragon Pass and founded Sun Dome temples in what later became Tarsh.
The “barbarian Sun god” (as the Dara Happans called Yelmalio) is neutral towards both Orlanth and the Seven Mothers, and is perfectly willing to serve as mercenaries for either. However, the cult views the Red Goddess and Shargash as enemies.
The biggest event of the cult was the refounding of the Dragon Pass Sun Dome temple in 1575, with the support of King Tarkalor of Sartar. Yelmalio templars fought bravely beside their king against the Red Emperor at the Battle of Grizzly Peak. Despite this, the Provincial Overseer in Mirin’s Cross strongly supported the Yelmalio cult as a counter-weight to Orlanth.
Now way out in Prax, the Sun Dome temple there maintains a meagre and seemingly absurd isolation, but elsewhere the Yelmalio cult is fully in the fray. The cult has a deserved reputation as unnecessarily aloof and holier-than-thou but that does not prevent them from fully participating in the wars and politics in Dragon Pass and the Lunar Provinces.
And if we think about the cult in the Second Age, Sun Dome mercenaries were a major military asset of the EWF from 750-1042 and fought against Carmania, Dara Happa, and the Middle Sea Empire.
The EWF encouraged the settlement of Yelmalion mercenaries at the edges of the empire.
By encouraging and supporting the Yelmalio Sun Dome temples, the Provincial Government is creating alternative power structures to the Orlanth cult in the Lunar Provinces, and Yelmalio does have a rivalry with Orlanth. The cult is a useful source of mercenaries for the Lunar Army.
That being said, the Yelmalio cult has shown on numerous occasions its willingness to work with Orlanthi leaders, and it has proven its resilience against the Lunar Way. That the Sartarites played the same game, and encouraged the refounding of the Dragon Pass Sun Dome Temple (and played a key role in the revitalisation of the Prax Sun Dome Temple), suggests that the cult may be a two-edged sword for the Lunar Empire.
A final comment – there are probably about 180-200k Yelmalio worshipers amongst the Orlanthi and Praians, another 100k among the Pentans, plus who knows how many among the elves (actually I could look that up but haven’t the time here). That makes it a pretty big cult (although definitely dwarfed by Orlanth, who has over a million cultists).