- Soul: A soul is... basically, you! A soul is the culmination of one's thoughts, feelings and memories. A soul is a source of spirit energy, and without it there is no life. A single soul can give life to a body, and an abundance of souls can give life to a whole planet.
Memories are a vital component of both souls and magic, and may accumulate and pass on across generations through a lifestream.
- Lifestream: A body of souls that permeates a planet's mana plane, from which new life springs and to which life returns when it expires. In high concentrations, lifestream may materialize physically in the form of crystal-like structures.
- Material Plane: The physical world and all its elemental components. All matter and chemical energy manifests here.
- Magic: A form of energy that connects spirit energy to the material plane. Its origins and applications are heavily-studied but still mysterious in many ways. Any being with a soul has the potential to use magic to exert control over the natural elements, altering the world around them.
- Crystal: A physical manifestation of spirit energy, named for its mineral-like shape and appearance. On the material plane, Crystals are special conduits of magic energy, and large ones may be attuned to specific natural elements [fire, air, water, earth], making the powers of nature accessible to mortals. On the mana plane, a Crystal resides at the core of a living planet and feeds the flow of souls through its lifestream, similar to the way a heart pumps blood through a body.
The Jewel of the Esper Realm is the Crystal at the heart of Genova, the neiphiti home-world, and is reputed to be a focal point for all Crystals on the mana plane, connecting them.
- Mortal: A living being made of a single soul bound to a physical body. Includes human beings and many sentient races dwelling on the material plane.
- Eidolon: A living being made of a single soul bound to a magicorporeal (made from magic rather than matter) body. Eidolons may be created from lifestream wells or mana pools [sprites, fairies], when a soul does not rejoin a lifestream after its corporeal body expires [fiends, ghosts], or by budding off other eidolons [monsters]. Not inhibited by a material body, eidolons have a greater capacity to use magic, yet are also more fragile than their mortal counterparts. Once destroyed, both the soul and body of an eidolon dissolve into raw spiritual and magical energy, respectively.
- Esper: An esper is created via either:
Espers command great spiritual and magical power, yet this power taxes their material bodies, and consequently they are unable to exist in the physical world for extended periods of time. Espers dwell on the mana plane until enough energy is acquired to cross into the material plane, and once this energy is spent they return. Binding one's soul to a relic is a way to facilitate these crossings and ensure the esper's connection to a specific location on the material plane.
A Great Esper is an esper that has ascended to the Esper Realm through a Crystal and acquired the power to cross the planes of existence at will. Great Espers have the potential to live eternally, their souls never decaying or expiring.
- Summoner: A mortal with the ability to communicate with spirits, up to and including the capacity to call espers into the material plane (espers call this ability makana.) The power required to summon an esper from the mana plane depends on the esper's strength, and may come at great cost to the summoner. Praying and using magic in conjunction with a relic is a safer method of summoning than relying on the summoner's own spirit energy.