Magic

Eko's magic is deeply tied to its cities, locations, and even some of its creatures.  Locations are tied to a specific element, and that elemental magic is most prominent there.

Elements are split into three groups: primary elements,  secondary elements, and tertiary elements.  Primary elements are basic elements which exist on their own.  Secondary elements are combinations of two primary elements.  Tertiary elements are a combination of a secondary element and a primary element.  Each element has its own role to play, whether primary, secondary, or tertiary.

Eko's main species can have an elemental affinity of any element they meet the trait or Manifestation requirements for, and indeed, many Manifestations are the result of an abundance of a specific type of elemental magic.  Having a Manifestation does not mean they cannot have an affinity which is not the Manifestation's affinity, however.