Thorns & Fire by Helen Scheuerer

A golden thread joined them, a bond that went deeper than love – and it had nearly destroyed them.

Wren Embervale and Torj Elderbrock share a dark and bloody history. With Thezmarr on the brink of another war, and overwhelmed by the force of their feelings for one another, Torj discovers there is far more to their bond than mere passion. The legendary Warsword is determined to protect Wren at all costs, even if it means lying to her . . . Even if it means losing her forever.
Meanwhile, Wren is struggling to find her place in the world – both as an advanced student of alchemy at the ancient academy of Drevenor, and as one of the heirs to a lost kingdom. With the midrealms once again facing destruction, Wren must decide: Loyalty or liberation? Legacy or love?
As new political players emerge, Wren discovers that her gift for alchemy is more powerful than she ever imagined – and that it could tear the kingdoms apart.

Will she and Torj find their way back to each other, or will the ancient magic that binds them become their undoing?