A city, presumably located in the Dreamlands, referenced in Curses of the Black Lake and Shards of Sight, two of the books in Lowls' footlocker.
In Chapter 125, Dora recalled some more information about Arventon:
The history of Arventon is relatively simple. It’s been defined, mostly, by what it’s NEAR. The city is perched on the edge of a great, dangerous mountain range populated by unknown riches and unknown terrors. It’s near a number of openings to the Dreamlands equivalent of the Underdark and VERY close to the mythical Black Lake and the Charnal Garden of Zura. But the city itself is known—mostly—as a bright, happy city of light, life, and learning where one rests, recoups, and stocks up before or after an expedition to one of the dangerous places nearby. It is the place to go in order to get the information one needs to foray into the mountains or the Underdark or the Lake. And that’s pretty much the story of Arventon.
Except…
There is the matter of the origin story of the city. Which… is not known. Because all record of it—in this city of learning and knowledge and preparedness—all record of the origins of the city were purged. But all traces… of hints… of possible ideas… that linger in the public consciousness all have something to do with a terrible Curse. Or, the threat of one. Something that will one day come to pass, PERHAPS, but only under very specific circumstances. And if anyone living, dreaming, or dead knows what that circumstance is, it’s not public knowledge.
In Chapter 126, the party arrived in Arventon to discover that the city had been frozen. Everything was completely transformed into crumbling yellow ceramic material, including its people.
In Chapter 127, the party learned scraps of information from a helpful Ghast about what happened to transform the city. Apparently a witch spoke the “secret name of Arventon” in the streets, one hundred years earlier. Some say she strode through the streets, hollow and empty, silver of hair, purple of eyes, trailed by a wretched fox. Some say she seemed like a god that had grown weary of her creations. Some say she wept. Some say she screamed. Some say she stared blankly, like a cold, dead statue. But when she spoke the name, the city changed forever. Everything above the surface of the earth turned to ceramic, except for some few people that became Ghasts.
The Ghasts were forced to dig their ancestors out of earth below their cemetery and eat them in order to survive. But eventually, Wamps moved in and pushed the Ghasts out of the feeding grounds. The Ghasts called out to their gods, but in vain. They then called out to the “spirit of the city,” which seemed to respond by periodically animating some of the ceramic statue-people to attack living creatures.
As they walked through the city later that chapter, the party saw evidence that the city had been highly technologically advanced (to a level not currently known on Golarion) and had been followers of the gods of the ancient Azlanti Empire.
First Reference: Chapter 90
Other Notable References: Chapter 101, Chapter 125, Chapter 126, Chapter 127, Chapter 128