I've been thinking about this for a while but to my shame I never actually thought of bringing this up on the forum until just now! So I'll try not to write an entire mini-novel about this, but the gist of it is that I've got a long-running RPG group of friends that I've run several games over what's coming up on a decade now, but we just recently started playing Pathfinder 1st Edition. I'm about to wrap up the Rise of the Runelords campaign, which is the first published campaign in the Pathfinder setting of Golarion. Anyone who's played the Kingmaker or Wrath of the Righteous CRPG games will be somewhat familiar with the setting. However, given the fact that Pathfinder's creators really went for the kitchen sink approach to their setting, including everything from Cthulhu to spaceships and androids to Narnia-esque accidental travel between Golarion and "real" Earth, I've done a bit of homebrewing in our group's setting. We plan to play more campaigns and each one will share the same universe, so to speak, and events and characters from campaigns they've played will influence what comes after. Other than changing some of the copyright-friendly elements back to what they were in D&D (Like making the Drow worshippers of Lolth instead of generic demon cultists, using Bahamut instead of Apsu, and having Mindflayers and Beholders exist in this setting), one of the things I've added is hints of lore regarding the Warhammer Lizardmen existing (or having existed) in the setting. Rise of the Runelords has a heavy focus on learning about the ancient past as powerful evil wizards who went into hibernation/magical exile 10,000 years ago are now starting to reawaken. The players in their adventures have come across a couple old ruins and references in ancient texts about how the world used to be ruled by a Lizardmen civilization (which was also a thing in D&D's Forgotten Realms setting) that has long since disappeared after a massive, world-altering catastrophe. The players have shown great interest in learning more about these ancient civilizations and perhaps harnessing some of their magical knowledge. We are going to play a different Pathfinder campaign with different characters next, but after that they plan on returning to their Rise of the Runelords characters to do some high-level adventuring, and in particular traveling to the lost continent of Sarusan. In the Pathfinder setting, the world map is vaguely based on the real Earth, but a bit more vaguely than Warhammer Fantasy's was. But you still have what essentially amounts to Europe with Africa/Middle Eastern countries below it on the map, North and South America to the West (called Arcadia) and Asian-themed countries to the East. The very vague equivalent of Australia on Golarion is an island called Sarusan. The only official lore about it is that it's a secluded place where few people ever go. People who have landed on it's shores have either never returned, or have awakened back on their ships days, weeks, or months later with no memory of what happened. However, people who have sailed close enough to get a look at it say that they've seen massive megafauna, including many creatures believed to be extinct in the rest of the world. It's said to be a diverse land containing dense jungles, expansive plains and harsh deserts. The seas around Sarusan are extremely dangerous and filled with constant storms and monsters. My players are very excited by the mystery of this land and really want to go there with their high-level characters in a future game. Needless to say, this sounds like the perfect place to use as the last bastion of the Children of the Old Ones! With this unexplored country having no real official lore, it's tailor-made to use in homebrew adventures and I'm hoping to come up with a fun, high-level campaign that would essentially be the equivalent of traveling to Lustria in the Warhammer setting! I know that there are some TTRPG fans here and I'd love to hear if anyone has any fun ideas or suggestions on what would be some fun campaign hooks for a place like this. If you want I can give my own headcanon lore about the Lizardmen in this RPG setting but this post is already huge so I'll put it in a reply if anyone's interested!
The Lustria source book for WFRP would be a good source of ideas. Sargava: The Lost Colony, Pathfinder Chronicles: Heart of the Jungle and Planeshift: Ixalan might be useful for generating ideas too.