The Prince of Souls by Lynn Kurland

One good deed leads to another, which for an evil mage desperately wanting to get back to his usual business of making mischief, is hardly a good thing.

Acair of Ceangail has, almost willingly, shouldered the quest of saving the world. Armed with nothing but his charm, a nose for trouble, and the determination to keep his beloved out of the magical fray, he’s marching off once again into the deepening gloom to engage in Noble Deeds.

Léirsinn of Sàraichte asked for magic, despite its devastating effects, to protect Acair as he seeks to fight a mage of terrible power and soul-draining spells. She just hadn’t expected her part in their quest to be quite so critical.

Time is beginning to run out for the two of them, and the battle to save the world and those they love draws ever closer. They just never dreamed how close to home that battle might be . . .