did you pull from the irl zodiacs when making the thirteen prime zodiac stuff or did you start ground up?
Yes and no. Good question.
Disclaimer: I do not subscribe to astrology of any sort. It's generally disallowed in Judaism, but your mileage may vary depending on who you talk to.
NOW ONTO THE ANSWER
I drew from the popularized Western, new age-y zodiac in as much as "vague predictions and assumed traits based on the sun sign when you were born" general concept.
After that I started making stuff up.
Any specifics for personality associations were based on a list of domains I had already pulled for mapping the Thirteen to deities for Solar Flare.
I also decided to use Cybertron's sun as one of the stars because that seemed appropriately counterintuitive.
And straight up having two "signs" (the Fallen & Liege Maximo) that people straight up don't talk about/ignore seemed amusing.
I also had Rodimus do it poorly on purpose based on how it tends to get used, so there is room to go "here's how the system he's allegedly using actually functions." He used the watered down stereotypes of how it works.
There's plenty of room for expansion, such as:
-vocabulary to describe people who fall under certain groups -stereotypes -what data/calculations are actually used to make predictions -how deep/complex varieties of the system can be (have you seen those complicated natal charts? holy shit) -whether or not it matters if you were forged or cold constructed -what the cycles of the stars are like especially since they live long enough individuals can actually see the which stars are visible in their sky changing as their solar system hurtles around the galaxy (do new stars get assigned the job? do new constellations get named and plopped in or replace old ones? does that change the understanding of that sign?)