Dragon Soul by LJ Swallow

A girl with dark magic who’s a threat to the kingdom. Three powerful men from the royal court. Why are they prepared to protect this daughter of shadow and take her to the heart of their realm?

The dragons are dead, the Ebon queen has destroyed the elven realms, and kingdoms are at war. The queen’s dark magic is growing in strength, and the Silvercrest kingdom is losing the battle against her. Three men are sent from the army’s stronghold to seek others who can aid their cause.
Leander, a high-ranking and domineering nobleman. Rohan, a fierce and seductive warrior. Galen, a gentle and passionate elven leader. Their task: recruit the most potent magic users from the shire towns and train them to join the crusade against the Ebon queen.
They never expected to find a daughter of shadow.

Calla’s time working at the apothecary in her small town is about to end, but not in the way she expected. On the day her magic skills are tested, she is revealed as a shadowmancer, a school of magic banned throughout the kingdom. A confused Calla faces a death sentence, but the three men are intrigued by the beautiful girl and her mysterious dragonkin pet and smuggle her from the town.
With no other choice, Calla journeys to the stronghold with the three captivating men. As they fight their way through enemy territory, the men discover that Calla’s power is more dangerous than they realised—and so is the bond this creates between them all.