Anya and the Nightingale by Sofiya Pasternack

After embarking on a journey to bring her papa home from war, Anya discovers a powerful forest creature who attacks travelers with weaponized sound. But she soon learns that he’s not the monster the kingdom should fear. There’s an even greater evil that lurks under Kiev. Can Anya stop the monster, save her papa, and find her way home? Or will the secrets of Kiev leave Anya and her friends trapped beneath the city forever? In Kiev, Anya and her friends find themselves involved with an aggressive elf, an earnest archer, and a bellicose princess. But who is the real monster?