The Kingdom of Regulus is enjoying a period of peace won by its general, the righteous Magnus, and his wife, Knight Commander Kera. However, that peace is shattered when the king is nearly assassinated during a diplomatic exchange with the far-flung Republic of Lyrium. When the Lyrian government pins the blame on a group of disaffected magic users, the Regulan royal family recruits Magnus, Kera, and a mercenary outfit to journey across the sea and work with the Lyrians in apprehending the masterminds.

Once they arrive, they discover that not everything is as it seems in Lyrium. Research into terracite - mysterious crystals capable of producing magic - has yielded technological and societal upheaval, displacing the skilled mages who once commanded government and industry. The Lyrian government now openly persecutes those who practice magic, forcing some families to flee from its terrible grasp and others towards violent rebellion. Meanwhile, the republic is expanding its borders into territory occupied by barbarians calling themselves the Ashen, hoping to secure more terracite for nefarious ends.

When one family - with connections to both the magic wielders and the Ashen - falls into Magnus and Kera’s orbit, the couple finds themselves drawn into the mages and barbarians’ respective fights, while dealing with lingering wounds of their own. Along the way, they will unravel a conspiracy within the Lyrian government, discover the origins of terracite, and grapple with an ancient prophecy in order to prevent a vengeful power from returning to prominence.