Firebrand by Kristen Briatain

Karigian G'ladheon returned from Blackveil broken physically and emotionally.  She also came with a mirror eye that shows the past and future to ones that view it.  The castle is attacked by an ice elemental, sent by Grandmother of Second Empire, and of course she is in the middle of the turmoil.
Even though she is not truly recovered she is sent with an Eletian to look for mythical creatures from their dark past.  Traveling with her is also her friend Estral who looks for her father, The Golden Guardian.
After she leaves King Zachery disappears leaving Estora, heavy with twins, to run the country.  That little fact gets very interesting as far as Riders are concerned.
Enough about the story line, the really important part of this review is the writing.  Things got so intense several times I had to stop reading.  Of course though that lasted for just a short time before I was called back to the book. I had also thought this one might end the series but the ending left more questions than answers, including the reappearance of a character that had not appeared in all of the previous 800 pages.  Cliffhanger!