This is a good question but the long and short of it is we don't know.
While the various atma are named after figures of the RL western zodiac, Jalzahn describes their formation and function rather simplistically.
So they may be named after Thavnairian gods, constellations, or figures from legend, but without a bit more lore it's a big question mark. Eorzean and Sharlayan astrologians follow many constellations in the heavens, but those of the western zodiac aren't mentioned to my knowledge.
Here's a couple more threads you might find informational, but neither has a direct answer to your question unfortunately.
-Hydaelyn Zodiacs
-Thavnair Lore
While the various atma are named after figures of the RL western zodiac, Jalzahn describes their formation and function rather simplistically.
Jalzahn Wrote:Now, I trust you are aware that aether permeates all things in our world. What you may not know, however, is that aether is found in greater concentrations in Eorzea than elsewhere. When a weapon infused with a quasi-soul such as your relic is used to slay a living being in this aether-rich land, a peculiar phenomenon occurs. The aether released by the fallen creature resonates with your weapon, and agglomerates into a crystal which I have dubbed “atma.†It must be noted that this occurs only on rare occasions, due to factors I have yet to identify.
Now, as you may have already gathered, atma is essentially the crystallized soul of a living being. And these crystals hold the key to strengthening your weapon. According to my research, twelve unique pieces of atma are required, meaning they must be acquired from twelve different foes. See the deed done, adventurer, and you shall hold in your hands such power as you have never known!
So they may be named after Thavnairian gods, constellations, or figures from legend, but without a bit more lore it's a big question mark. Eorzean and Sharlayan astrologians follow many constellations in the heavens, but those of the western zodiac aren't mentioned to my knowledge.
Here's a couple more threads you might find informational, but neither has a direct answer to your question unfortunately.
-Hydaelyn Zodiacs
-Thavnair Lore
