Check out this awesome summary from the Zodiac Books website!
The Zodiac Galaxy is comprised of Twelve Constellations, or Houses, that revolve around the great galactic sun Helios, each one named and modeled after a Zodiac Sign. There is a legend of a Thirteenth House—Ophiuchus, the Thirteenth Zodiac Sign—but by now the story has been told and retold for so many generations that it’s regarded as nothing more than myth.
Scientists believe Helios marks the site of the original Big Bang that gave birth to the Zodiac, and therefore everyone is taught that Helios is the anchor to life, though each House holds its own spiritual beliefs about it. History tells us the original human colonizers came from a distant and long-gone planet called Earth, and they traveled through a portal in Helios to get here—but the portal is just another myth. Like the Thirteenth House, no one believes it’s actually real.
By the time Earth collapsed, scientists had found a passage into another universe that might sustain life. The surviving members of our species came together and set off to find this new home, and when they crossed the portal into Helios, they first settled on Aries and later spread to the other Houses. When the Thirteen Constellations of the Zodiac foresaw the first people arriving through Helios, each House gave up its Guardian Star. The shooting stars crashed onto planets in their own Houses, and they arose human, each with a Star Stone, or a Talisman, that stored their particular power—the strength they bring to the Zodiac. Each Star was the original Guardian of his or her House, and in human form they were now charged with harnessing the powers of their Stones to protect their planets and people.
Of all the Guardians, the Thirteenth, Ophiuchus, was by far the most welcoming of the humans, and in the end it was he who convinced the newcomers to give the Guardians a chance.
Once the settlers decided to go with the Guardians, each shared what strength he/she most valued and described what kind of world his/her House would one day be. The Earthlings were free to follow whomever they chose and set off to colonize their new worlds. Over time, people evolved according to the environment around them: On Cancer, everyone’s eyes started to reflect the Cancer Sea; in the mines of Gemini, people developed tawny skin; on Aries, they were built like soldiers; and so on.