In Greek mythology, Hercules and his plucky nephew Iolaus kill the Lernean Hydra—a massive serpent with nine regrowing heads—by bashing and burning eight of its domes and then slicing off the ninth.

Everyone knows the legend of Hercules and his twelve labors. Our story begins after the labors, and after the legend. Haunted by a sin from his past, Hercules has become a mercenary. Along with five ...