Kandrith Series by Nicole Luiken

Sarathena Remillus, daughter of the newly elected Primus of the Republic of Temboria, has been given a mission: discover the secret of slave magic. Anxious to escape the corruption and treachery of the capital, Sara welcomes the chance to finally prove herself far away in Kandrith, the tiny nation of former slaves. Accompanying her on the journey is Lance, a Kandrithan to whom Sara owes her life... moreSarathena Remillus, daughter of the newly elected Primus of the Republic of Temboria, has been given a mission: discover the secret of slave magic. Anxious to escape the corruption and treachery of the capital, Sara welcomes the chance to finally prove herself far away in Kandrith, the tiny nation of former slaves. Accompanying her on the journey is Lance, a Kandrithan to whom Sara owes her life. Lance despises the nobility, and is determined to resist his desire for Sara, despite her attempts to entice him into divulging the secret of his magic. Soon their travels become fraught with peril, and Sara discovers she's fallen victim to the ultimate betrayal. To end a war between two nations, she will have to make the ultimate sacrifice... 134,000 words less

The conclusion of the Kandrith duology Lance is a healer and wielder of slave magic, a power that demands sacrifice. He gave up his health to gain the ability to heal others, but he's powerless to cure his beloved Sara, who sacrificed her soul to save Lance and all of Kandrith. Returning her soul would negate her gift, at the cost of his life and the freedom of his homeland. Now Sara is but a shell of the noble, spirited woman she once was... moreThe conclusion of the Kandrith duology Lance is a healer and wielder of slave magic, a power that demands sacrifice. He gave up his health to gain the ability to heal others, but he's powerless to cure his beloved Sara, who sacrificed her soul to save Lance and all of Kandrith. Returning her soul would negate her gift, at the cost of his life and the freedom of his homeland. Now Sara is but a shell of the noble, spirited woman she once was. All that Lance saw and loved in her is gone, but he refuses to give up on her. Charged by his sister, the ruler of Kandrith, with a mission to encourage a budding rebellion within the aggrandizing Republic of Temboria, he leaves with Sara in tow. But not before Wenda's soulsight detects a spark within her. Amidst the escalating dangers in hostile territory, Lance will have to risk both his beloved and his homeland in a final gambit to save them both… 138,000 words less