*update* 
 Ok I was really angry when I first wrote this review and I've had time to rethink about the ending. The book itself was still a disappointment but the ending was more satisfying that I had given it credit for during my first reading. It remains flawed and I still feel like the author owed us more than she has given us but at least she made an effort and, although it could have been better, it could have been worse. 
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 Somewhat of a disappointing final installement for a series that started with a great, original story. There were many good elements in this book, it was beautifully written and the emotional rollercoasters were still there - hence why I gave it 3 stars. 
 I cannot blame the author for everything that I have disliked in her book since it is her universe after all, but it definitely wasn't perfect and many things could have been done better. 
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 Here is what bothered me the most: 
 1)Kicking out the PROTAGONISTS out of the spotlight. WTF? 
 Whereas I expected a book about Karou and Akiva, I got a story focusing on side characters. 
 - A. Two Fallens the author obviously wanted us to feel sorry for; 
 - B. One other character named Eliza, who reminded me of 'The Vision' from Avengers 2 - a random character put into the story for the sake of blurting a solution to everything. 
 There were SO MANY chapters about some those annoying characters that I couldn't give two quacks about. Am I supposed to care about 10 chapters of Eliza's job as a DNA scientist/ or whatever her job was? NO. And her colleagues and rivals? Um, no. Where are my chimaeras? 
 2) Cliches of Humans & Prophets 
 The introduction of the Seraphims to the Humanworld was splendid, intelligent and somewhat realistic. I could totally imagine people reacting to Seraphims like that. I was really excited about it and I did fear for the well-being of Eretz. 
 But. 
 Laini Taylor had too add a prophet and crap to it. Really? Don't we get enough of that bullsh*t in Tv Shows, games, books and during school classes? All the plot surrounding that Prophet-character was unnecessary and aggravating. She could have just been introduced as a random character - which she was - and the main characters could have just met her where they did in the book without all the boring plot surrounding her. 
 This together just made the pacing of the story horrible. 
 3) The Stelians 
 BOY WHAT I DISAPPOINTED. My expectations of the Stelians and their role were definitely too high. Throughout the whole story, I thought that they would be these powerful, peaceful magi-Seraphims that lived with Chimaeras in the Far Isles and I was expecting Karou and Akiva to go to them for help. 
 Nah, they were just there to postpone What Should Happen between Akiva and Karou. Oh their queen is a bitch-whose-face-needs-to-be-ripped-off-by-the-darkness-hopefully-in-a-possible-sequel-please. Even if 50%of her bitchyness was justified. 
 4) The lack of closure 
 If you were expecting an ending that would have given you an insight on the characters's lives after the War and see how they would build a world together, well... None of that. You don't get to see how they've bonded and the things they will do together (aside from Liraz and Ziri) and their plans for the future. 
 I wanted to hear about the laws of the new world, of that post-Empire era and NOPE NONE OF THAT. Only a glimpse. A glimpse of something I've been waiting for since the first book. 
 Instead of closure, the author gives us a half-assed new subplot with enemies introduced by the Stelians. Some monsters. A darkness that devours worlds. Now where have we heard of that before, hmmmm. If you don't want to end a series, just invent some new threat and blame the darkness - it always works ! 
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 Overall, it was an ok book. Even if I skipped 25% of it because those chapters were irrevelant and aggravating. 
 I'm butthurt because authors often think that they need to make a happy-limit-sad-and-bewildering ending to make a series 'good' and 'memorable'. This 3rd book had so much potential and I feel like the author ruined it by focusing on irrevelant characters instead of the main characters. 
 As for the conclusions, it could also have been better had Laini Taylor focused on the now and the after instead of introducing us to a new threat. It was too soon and I feel like she owed us a good 10 chapters of And then about our characters and the new world they've built before jumping to the next war in line - possibly to extend the universe. 
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 Nonetheless, if you have read the first two books, you'll have to read this book. It's the author's book, her universe and characters, even if it means disappointment for us. 
 It was still a beautiful experience and I don't regret having read it. Hopefully, she will pursue the adventures of Chimaeras, Seraphims and Stelians in some other series - and if we're lucky - some of our characters will make an appearance in those other books.