With apparently minimal effort (I do always forget I can text search individual works on archive.org), I've learned about the Madrian 13-sign Zodiac. I'm a bit disappointed to find out there aren't unique signs, or reinterpretations of the signs, but this is still interesting. This appears to have been an idea that was circling around the late 1970's pagan scene, as a 1977 book seems to explore this idea. This particular book can also be borrowed on the internet archive here. This book appears to call her "Queen of the Zodiac", and the Madrian source apparently refers to her as "Rule of the Zodiac", so presumably this book would have been the inspiration for the 13th Madrian sign.
A little further research turns up this page, which states that Arache Rising was written by Sci Fi author John Sladek as a bit of a hoax that took of a life of it's own. It's also worth pointing out that a more modern idea of a 13th zodiac sign has been introduced with Ophiuchus, but Ophiuchus is in a completely different place in the Zodiac.
