This was very easy. I didn't really have to think hard. Here are the book names:
Prequel: Blade of Fire
First book: The Shattered Throne
Second book: Crown of Shadows
Third book: Path of Midnight
Last book: Realm of Death/Blood (whichever one your prefer)
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If you guys want to give me some good titles for the prequel, I would be happy for suggestions. I just came up with one.