Wildfire by Mila Young

If Luna thought her first month at the Guild of Shadows was tough, then she’s in for another ride.
Her guardians are deadest on unlocking the information her parents buried in her mind, believing it to be the key to defeating the Serpent Brotherhood. Except Luna’s finally found somewhere to settle down, a home, and answers to the questions her parents hid from her. The last thing she wants is to jeopardize that by releasing the evil inside her.
But she can’t escape her past when the Brotherhood is siphoning the power of the veil, weakening it, and allowing all sorts of terrors through to Earth to keep the guild busy in fighting them.
Enter Gable, the dark and mysterious runaway from the brotherhood. One of the enemy baring the same tattoo as her. The last person she wants to align herself with. But he might be everything she needs. The way to defeat the threat against the guild. Or he might be her downfall.