After troll magic closed Old Pavis, constant struggles occurred between the dominant trolls and the remnants of humans, elves, and dwarfs. The Pavis cult held to its rituals, and their intimate knowledge of the city aided worshipers in every crisis. the cult kept non-troll dwellers alive in the ruins until the city was re-opened during the time of strange magics and phantoms from the past known as the Dragonewts Dream.
To me this is key to understanding the survival of non-trolls in the Big Rubble. Pavis provided them with small elementals and City Harmony (which reduced how aggressive the trolls were in hunting down humans), but most important was knowledge of the ruins, tunnels, and byways of Old Pavis.
So imagine after Gerak Kag conquered Old Pavis. The humans fled to their remaining strongholds, which were connected by tunnels (which dated back to the centuries of struggle against the nomads). This information would be recorded in Old Pavic or Auld Wyrmish – and meant the Pavis priesthood needed to remain literate. But this literacy is purely practical or traditional – a way for such necessary information to be maintained.
Remember, there were likely only around 1000 humans in the Big Rubble during the Troll Occupation. There was little communication or trade with the outside world – the trolls sealed the gates. Weird cults and spirits like Black Fang were embraced because they enhanced survival. This was a dark time.
For the elves and dwarfs it was also difficult, but not as bad. The elves let the Garden grow wild and maintained a community of 1000 aldyrami, of which just over 200 are actually elves. They remained allied with the Pavis cult.
The dwarfs had it easier. The some 200 dwarfs had iron weapons, and even more knowledge of the tunnel networks than the Pavis cult. With the Flintnail cult, they were firmly allied with the humans of the Big Rubble.
And in that way they survived some three centuries of troll dominance. Things no doubt were looking dire when in 1539 the Troll Occupation was abruptly broken by the Dragonewt Dream. Eleven years later came the Sartarites led by Dorastor. The Wind Lord and his companions were powerful enough to keep the trolls and many Pavis Survivors chose to settle in his new city, Pavis-Outside-The-Walls.
In the present day, the cult of Pavis is mostly worshiped by lay members, who are initiates of Orlanth or other gods. Only lay members are allowed to become citizens, which entitles one to free food.
Initiates make up many of the city’s masons and stoneworkers, although not all initiates are masons or stoneworkers. Initiates cooperate closely with the Flintnail cult.
Remember Pavis himself no longer dwells permanently in the Real City, although he comes back to his temple every holy day. But his temple Outside the Walls is now the center of his cult.