Spice is a flavoring substance that, in some cases, are illegal and possessed a drug-like ability to affect the mind, mood and senses. When illegal spices were consumed in large amounts, it caused people to become twitchy and bug-eyed, acting violently towards anyone and anything around them and also made them extremely vulnerable to hypnosis.
Illegal spice was the major factor in the Klaww Gang's plans to take over Paris. Dimitri ordered the spice and distributing it via his nightclub through food ordered by his patrons. Rajan meanwhile, increased the spice growth in the jungle via using the Clockwerk heart to increase his spice production tenfold. The Contessa made use of the spice's drug-like effects, in order to increase her ability to hypnotize criminals held in her facilities, as evidenced when she forced Murray to eat food covered in spice, thereby making him feel "strange" and demonstrating hostile and violent behavior, when her hypno-boxes were turned on. Jean Bison would transport the spice across North America using his Iron Horse trains. Arpeggio and Neyla both planned to fly over Paris in Arpeggio's blimp and use the high levels of spice consumed by the citizens below along with a hypnotic light show powered by the Northern Lights to hypnotize the whole city into generating high levels of hatred in order to restore Clockwerk's immortality.