Roman era historical fiction with horror crossover

When Roman Pomeria collapses in a single, blood-soaked night, two lives are changed forever: Marcus, the hard-bitten ex-centurion sold as a slave and Laysa, a spirited half-Berber girl mourning her lost family must flee through hostile lands. Under the shadow of a world collapsing around them and the stench of the dying, they must create a new family from shared danger and mutual vows.

Decimus the young tribune in his first command must fortify walls, improvise weapons, and, as the fires climb, make impossible bargains. The real enemy is not only the shambling corpses but the cost of leadership: which lives to save, which to sacrifice.