Give Way to Night - Cass Morris - Bog

The second book of the Aven Cycle explores a magical Rome-inspired empire, where senators, generals, and elemental mages vie for power.
Latona of the Vitelliae, mage of Spirit and Fire, is eager to wield her newfound empowerment on behalf of the citizens of Aven--but societal forces conspire to keep her from exercising her gifts, even when the resurgence of a banished cult plots the city''s ruin. To combat this threat, Latona must ally with Fracture mage Vibia, the distrustful sister of Sempronius Tarren.
While Latona struggles to defend their home, Sempronius leads soldiers through wartorn provinces to lift the siege of Toletum, where Latona''s brother Gaius is hemmed in by supernatural forces. Sempronius must contend not only with the war-king Ekialde and his sorcerers, but with the machinations of political rivals and the temptations of his own soul, ever-susceptible to the darker side of ambition.
Though separated by many miles soon after their love affair began, Latona and Sempronius are united by passion as they strive to protect Aven and build its glorious future.