Ash Walker. Blood Sea Tales, #4

Nothing is more damning than a deal with death. In lawless Haven, a fearsome reputation means safety. Wielding necromantic powers not only keeps Hashi Severn alive, but provides a comfortable life, a seat on the Haven Council of Lords, and the opportunity to indulge her passion for history. No one willingly crosses the woman who wields the dreadful obsidian dagger, Soul Drinker. That is, until Jhavika Keshmir attempts a coup, destroying Hashi's painstakingly structured existence. Now Hashi must embrace what she's avoided for years-alliance.
Only together can the surviving council members prevail in a war against an army of enscorcelled slaves. But trusting in others is risky, because Hashi harbors a terrible secret, one that threatens not only her life, but her very soul. For dealing in death comes at a terrible cost.