The Empyrean Series Collection 3 Books Set By Rebecca Yarros (Fourth Wing, Iron Flame & Onyx Storm):

Fourth Wing:
FRIENDS. ENEMIES. LOVERS . . .EVERYONE HAS AN AGENDA.Violet Sorrengail expected to live a quiet life surrounded by books, until she was forced onto the world's deadliest training ground. Now she must fight to join the army's elite: dragon riders. But dragons don't choose fragile riders, they incinerate them, and when your body breaks as easily as Violet's does - death is only a heartbeat away.Many cadets would kill Violet to better their own chances of success; the rest would kill her just because of her last name . . . including the ruthless Xaden Riorson, her family's greatest enemy.

Iron Flame:
Against all odds, Violet Sorrengail made it through her first year at Basgiath War College, but now, the real training begins. The stakes are higher than ever, and a determination to survive won't be enough this time.When a powerful new enemy threatens everything she cares about, including the man she loves, Violet must do whatever it takes to keep their secrets safe. One wrong move could have horrifying consequences - and as the web of lies spun by those in charge starts to unravel, nothing, not even dragon fire, may be enough to save them in the end.

Onyx Storm:
ARE YOU READY TO BRAVE THE DARK? After nearly eighteen months at Basgiath War College, Violet Sorrengail knows there's no more time for lessons. No more time for uncertainty. Because the battle has truly begun, and with enemies closing in from outside their walls and within their ranks, it's impossible to know who to trust.Now Violet must journey beyond the failing Aretian wards to seek allies from unfamiliar lands to stand with Navarre.