Larkspur, or A Necromancer's Romance - The Courting of Life and Death, #1

Clandestina is a realm of secrets and dark magics. Among the nobles there is talk of a goddess of death, and a forbidden magic she grants to those that follow her-cræft that can heal injuries that should be fatal or even bring back the dead. But she asks for much in return; blood and sometimes even life itself. Duc Pierre Salvador has returned to court after finishing his studies and becoming a surgeon.
But, as he flirts with his childhood friend Elizabeth Anne, another waits for him.Mora, The Lady of Death.