Now this was interesting to me. You see I went back to the Terrors of Athas, to double check the monsters that was in this book. Mythical Monsters Revisited, by Paizo/Pathfinder.
Imagine my shock when only one was in there! The chimera! No hydra! No harpies!
Quite a shock. So I’ll go through the monsters in the book and explain how they can be Athasanized… no that sounds too much like euthanized. Converted instead?
Chimera- There’s already been an awesome thread on how to make an Athasian chimera. It is already listed as an accepted monster. Where might they come from? Experiments by sorceror monarchs or Rajaat? Mutation by the Pristine Tower? Their classic role as a monster for heroes to prove their puissance against remains intact.
Coatl- A messenger from benevolent gods to guide young civilizations? Yeah, this one doesn’t fit. What I can imagine is a story with one waking up from a long sleep only to see the lessons he taught resulted in such disaster. “But I showed that Rajaat fellow just a few cantrips!” Of course, that’d be bonkers on the lore.
Griffon - This one is iffy. I don’t see it conflicting with Athas by itself. It looks too much like standard heraldry on it’s own. The best use of a griffon in Athas in my opinion. Change it cosmetically and give it a different name. Don’t tell the players it’s a griffon. “Is that a giant dragon fly with the front of a giant Kestrel?”
Harpy - Okay, I’m more serious about this one. Once again, would want to change them visually, liken to kestrels and the like. You can easily give them character levels, like psion. Someone may point out that harpies would have a role similar to belgoi. AKA man eating monsters that lurk in the wilderness, entrapping the unaware through music. I say take advantage of that. Have harpies the FEMALE belgoi. The belgoi males compete to bring her the best offerings (sentient or otherwise), to win mating rites.
Another element that could be explored would be as a dark element related to the aaracockra. Perhaps a brutal feud, warring over potential roosts…
Hydra- They are typically thought of as living in swamps and marshes. However, it requires little to no effort to make them suitable to dryer climes. A few visual touches, and BAM! Athas ready.
If you are looking for something more intense, think SILT hydra. Ideal for players who think they are experts in silt horrors. It can hide beneath the silt, with nostrils just above the silt. The heads lash out when prey gets close. Given that new heads would be growing beneath the silt unseen by players, they simply may not realize they are dealing with a hydra.
Kraken - I do want to strongly state this first. SILT DOES NOT EQUAL WATER. It is very different, especially in the hands of a good story teller. Kraken would be easily added, if one was so inclined. It’s mostly a question of having a super intelligent silt horror. Like the hydra above, it can be a new twist on a familiar monster. The book does have a lot of lore and cool extra ideas. A lot wouldn’t move to Athas all that well, though.
Sorry folks. Will finish this tomorrow