Daughter of No Worlds by Carissa Broadbent (The War of Lost Hearts, 1 of 3) [Hardcover]

Tisaanah spent years as a slave in the Threllian Empire and got out by being more stubborn than the people who owned her. She arrives in the Orders of magic with untrained power and a plan: become a mage, return, and free everyone she left behind.

The Orders give her Maxantarius Farlione. He is brilliant, retired by choice, and wants nothing to do with students, wars, or the past that made him leave. He agrees to teach her anyway. It takes them both a long time to understand why.

This is the series Carissa Broadbent wrote before The Serpent and the Wings of Night: slower, deeper, and built on a romance that earns every step. Book one of three. Bramble hardcover edition. New and unread.