6 decades books

Long ago, humanity saw more than the world before them. Dragons once filled the skies, spirits walked beside forests, and beings from higher planes shared their consciousness with humankind. But when humans tried to steal that power, an entire race was wiped out. The skies fell silent. Now humanity lives blind to the hidden universe around them. Until a mysterious girl meets a boy carrying the unintended result of that ancient tragedy. And somewhere beyond the visible sky, an angel named Azazel is preparing his revenge.