The Poison Master - Liz Williams - Bog

Enslaved on an isolated planet, an alchemist fights to free her sister-and mankind
Latent Emanation is a cruel world where ordinary people do everything they can to stay out of the way of their vicious masters, the mysterious Night Lords. Apprentice alchemist Alivet Dee is more cautious than most, having devoted her life to making enough money to buy back her imprisoned sister from the Night Lords-but trouble is about to find her. When a client dies during a routine alchemical session, Alivet flees-pursued by the Night Lords, their minions, and a dark force that haunts her dreams.
She is rescued by Ghairen, a Poison Master from another world who offers her a chance to save her sister-and humanity, as well. He is charming and handsome, with ruby-red eyes that glow in the night-but how can she trust a professional assassin? As she proceeds warily alongside the Poison Master, Alivet finds a chance not just to save mankind, but to unlock the mysteries of humanity's very existence.