Beguilement

Description for BEGUILEMENT by Lois McMaster Bujold:

Troubled young Fawn Bluefield seeks a life beyond her family's farm. But en route to the city, she encounters a patrol of Lakewalkers, nomadic soldier-sorcerers from the northern woodlands. Feared necromancers armed with mysterious knives made of human bone, they wage a secret, ongoing war against the scourge of the "malices," immortal entities that draw the life out of their victims, enslaving human and animal alike.

It is Dag--a Lakewalker patroller weighed down by past sorrows and onerous present responsibilities--who must come to Fawn's aid when she is taken captive by a malice. They prevail at a devastating cost--unexpectedly binding their fates as they embark upon a remarkable journey into danger and delight, prejudice and partnership . . . and perhaps even love.

This is #1 in The Sharing Knife Series.