The Cloud of Darkness (The Ingenairii Series Book 11)

The decades of Alec's life together with Andi have brought peace and prosperity back to the Dominion and Michian. The two ingenairii, their minds and souls uniquely united, have shared dreams, memories, goals, and a lifetime of affection. But Andi's body is not as able as Alec's to self-heal and repair itself year after year, and she recognizes that her mortality is real.
When Alec takes her back to her childhood home, Riberte, a small village in the Avonellene Empire, she is at peace. But for Alec, it is the beginning of a whole new set of adventures, and battles against a foe that he doesn't understand.