Magic Knights
A Magic Knight is an individual who uses a certain type of magic. Magic is the manipulation and application of mana: A form of energy that exists in nature and within people. There are many types of magic that a Magic Knight uses, however, it is limited to one element per person: As everyone's mana possesses an affinity to one element out of the main four. There are many elements that come from the main four, so there are countless elements out there that many may use.
Since a Magic Knight is limited to their own elemental affinity, they cannot use magic that lies outside of their affinity. However, they may combine their own magic with other neutral forms of magic such as combining wind magic with creation magic, or plant magic with healing magic. This increases their versatility, as there are several neutral types that may be used in conjunction with one's affinity.
Uniquely, under unknown circumstances a Magic Knight can be artificially enhanced to be able to use more than one affinity of magic.