The Digging Witch by KB Lawrence

In Icegrind, your secrets will kill you quicker than the cold... Libby Scarpa, prized witch of the most vicious criminal on the ice, is tired of digging through the secrets of smugglers. She has plans to sneak past the city wall and make her way to a new life. But an old friend finds a trove of maps that could rekindle an ancient war—a war the undying won, and which nearly wiped her kind from the ice. And Libby must do one last job. To save towns that have never sheltered her and people who have only feared her—and to keep a promise to a friend—Libby must cross a ghost-haunted glacier, evade an army of immortals, and rely on a man whose secrets are hidden, even from her. If she can embrace her power instead of fear it, she might be able to get the maps to someone powerful enough to save everything she's come to love.