Renegade: Book 3 (Hell's Underground)

Paul has met his most audacious - and powerful - ancestor yet, Samuel Rector, who seemingly has the entire East End in thrall to him in the 1830s. His legion of 'rat boys' use terror and menace ordinarily, but with the demon seed inside them, their powers know no end. Their only match is Paul, the renegade, the one member of the Rector clan determined to strike each poisoned generation from the family history. But nobody is stronger than Lud, the King of London, struggling against imprisonment in his cell where the city's five gates meet.