Set in an alternate world; humans, gods, and spiritual beings known as "Katenas" coexist. Katenas are powerful warriors with the ability to encase themselves in full suits of armor called "Lexes". The Katenas are the envoys of the gods. The three great Katenas, chosen by the gods, are collectively referred to as "Oz".

Both humans and Katenas are overseen by the gods. As in Greek mythology, the gods are described as omnipotent, ambitious, self-serving, and power-hungry. The major source of their power is light; as they consume light, they cast parts of the world into darkness for centuries. The gods seek to destroy humanity and drain the planet's energy source, "Etheria".