The Trials of Darkness by Kathryn Breaux

For years after her mother’s passing, Briar Blackbyrne lived in the shadows.

Briar now lives her life completely invisible to the outside world and her father, who rules the kingdom of Daramveer through fear and punishment. The princess of this feared kingdom has a darkness within her that keeps her chained and afraid of losing control.
Being descendants of powerful Gods and Wiitches, Shadow and Lumor Wielders are gifted with magic. Or so some think. When Briar’s mother died, so did her magic, as she vowed to never use her curse again.
When Briar’s brother returns to the kingdom of Daramveer after being away for five years, things begin to change. Unexplained creatures from Briar’s past, ritualistic crystals, and a dark ancient magic begin to surface that should have long been forgotten. When the king announces an arranged marriage, Briar decides to fight for her future and her own hand by entering a number of deadly trials alongside the men fighting for her.

Winning the trials turns into a distant thought, as merely surviving becomes the true test.