Citadel
(Book)

"Citadel is the only human city on the alien planet Edalide...But the drowning waters, constant threat of starvation, and eternal cold aren't the most dangerous challenge. For the Flooded Forest is ruled by demons: monsters from Hell sent by their vengeful god...To save their souls and return to their former glory, Citadel must kill every single one. Olivia lost her lover to the demons almost a year ago. But during a scientific expedition, a chance encounter reveals that the demons are sentient--a startling discovery that would get Olivia executed if she exposed it"--,Provided by publisher.