A Ballad of Severed Souls by Jodie Angell

Adelina Orlova is the long-lost wielder of astral magic. Filip Tarasov is an influential sorcerer of nether, and after a decade of searching, he’s finally found her. Each wields a half of soul magic and neither can be at their strongest without the other. When Adelina’s dormant powers are forced to the surface, she helps Filip with his plans to reunite the divided countries. But in doing so, she must leave behind Damir, the man she’s falling for.
When Adelina discovers Filip wants to force her into marriage to secure a powerful bloodline, she hastily marries Damir instead. Adelina must walk a blade’s edge between bending to Filip’s will and conspiring to overthrow him. Everything she holds dear is at stake, including the man she loves.