In a world where the dragon-ruled Kingdom of Amelia holds a monopoly on magic and uses it to crush neighboring nations, the small iron-and-fire land of Campusfellow faces inevitable conquest. Desperate to survive, Lord Bud Grace devises a last-resort plan: ally with the witches—terrifying beings of legend whose powers rival Amelia’s sorcerers. To execute this plan, he dispatches Rollo Duvel, an assassin raised from childhood as a weapon and known as the Black Dog, who is versed in every method of killing. Rollo’s mission is to track down and secure seven witches scattered across the continent, beginning with the Mirror Witch, a figure surrounded by rumors of massacre and calamity. When word arrives that the Mirror Witch has been captured in the neighboring kingdom of Levee, Bud and Rollo set out to take custody of her, setting in motion a dark fantasy of war, political intrigue, and uneasy alliances. As Rollo confronts beings even more dangerous than his usual targets, he must navigate a world where magic is a tool of domination and witches are both feared and exploited, forcing him to question the line between weapon, monster, and ally.