In this historically inspired world, health, technology, and powers are all tied to the four body humors: blood, bile, black bile, and phlegm. Descendants with cursed humors have control over the elemental power within their body fluids. These are the Magus, revered, feared, and forced to live in the shadows of the developing world. They and humanity struggle against each other, and the creatures that hunt to consume their humors.

In the town of Deltador, a quiet traveler arrives, absent of any caravan for protection from the beasts outside the gates. A young girl seeks escape from the monotony of the town. Their paths cross and fate is changed; nothing will ever be the same again.