Entangled Souls. Soul Mates, #1

Seven thousand years after the Dark Lord unleashed his Darkness upon the Continent, in grief, killing millions-a new Lady of Light is born, a doppelganger of his lost love. When she comes of age, her inner Darkness calls out to the immortal and jaded Nox. At the sacred Day of Love celebrations by the River of Souls, Nox risks his life to save hers, breeching the magical barrier that keeps him out of the North, defying the Goddess.
In that moment, he unknowingly sacrifices a part of himself, sharing his immortality with the young queen, Astra, and entangling their souls forever after.