The Midnight Beast by Matt Hart - Children's Book

The Scarp. Also known as The Emporium of Human Misery. A savage demon is stalking its streets. A powerful secret society, the League of the Golden Unicorn, is bent on restoring the monarchy. Could they be inciting a revolution from the bowels of the city?

Meanwhile, Lord Bortle, a member of the League, wants to create a Fabulary Garden full of fantastical creatures from the underworld... and all he's missing is a werewolf. The demon Bazimaal knows where the werewolf is hiding: in the house of the famous conjurer Callisto.

Crispin, Callisto and a feisty new river-girl, Dessica Flaunt, must crack codes, reclaim the werewolf and return the demon to the underworld, before Bazimaal triumphs and the Scarp is utterly destroyed...