Black Moon by Russell Romina

One final secret stands between Rho and the enemy. But will the devastating truth destroy her first?

Rho, the courageous visionary from House Cancer, lost nearly everything when she exposed and fought against the Marad, a mysterious terrorist group bent on destroying balance in the Zodiac Galaxy. Now the Marad has disappeared without a trace, and an uneasy peace has been declared.

But Rho is suspicious. She believes the Master is still out there in some other form. And looming over all are the eerie visions of her mother, who died many years ago but is now appearing to Rho in the stars. 

When news of a stylish new political party supported by her best friend, Nishi, sends Rho on another journey across the Galaxy, she uses it as an opportunity to hunt the hidden master and seek out information about her mother. And what she uncovers sheds light on the truth--but casts darkness upon the entire Zodiac world.