Maelstrom (Book V of the Winter Fire Series‪)‬

As the battle between Bren and Loki rages, Jenna finds herself powerless to stop their fury from spinning into a force more destructive and deadly than anyone - human or god - could have foreseen. Now, in a race to keep the danger from swallowing up their world, they must descend into an abyss of space and time, where each new revelation rolls into a deeper mystery.