The Villainess Captured the Grand Duke

When Han Seo-ah wakes up as the villainess of a novel, she knows her fate: execution for trying to poison the female lead. Desperate to survive, she proposes a contract marriage to the fearsome Grand Duke Cédric von Löwenstein, a man even the emperor fears. In exchange for protection, she'll use her knowledge of the original story to help him uncover a conspiracy threatening the empire. But as she spends more time with the cold-hearted grand duke, she realizes that behind his icy exterior lies a man who might just be her greatest ally—and perhaps something more. (Source: Webtoon Entertainment)