In previous versions of Phantasy Star, "photon" was a mysterious energy that could be harnessed  for a wide variety of purposes such as improving weapon efficiency. Photon plays the same role in Phantasy Star Universe, but its uses have been expanded. This guide will give a brief overview of the role Photon plays in Phantasy Star Universe. You can jump to the section you wish to read by clicking on one of the following links:

• Overview
• Photons and A-Photons
• A-Photon Reactor
• Shield Line System
• Nanotrancer

Photon is a type of energy that has become the foundation of modern science in the Gurhal System. The surface of the planets as well as the air and space around them are all rich in photon particles. Needless to say, ordinary people are incapable of sensing their presence, however those who respect or view photon as a spiritual energy possess the ability to produce techniques through the catalytic properties of photons.

Photon energy is the most commonly used source of energy in the Gurhal System. Photons are extracted from the air, transformed into energy by devices such as photon reactors and photon drives, then put to practical use in a variety of ways. The resultant energy can be used to miniaturize extremely large objects and is used by the Guardians in weaponry as well as vehicles. The output of photon energy is also manipulated in other ways in order for some people to receive greater spiritual influence from it. Even when the same reactor is used, there will always be an obvious difference in output between an expert in the field and a beginner.

Being confronted with the issue of unstable photon output, some people developed a new type of energy known as advanced, or A-photon energy. Despite the characteristic high-level energy output of A-photons, people have accepted that the energy can be stabilized and put to practical use. Over the past 15 years, use of A-photon energy has become greatly widespread.

A-photon energy and photon energy actually do not share that much of a relationship. Photon particles put through an extremely advanced and unique refinement process yield A-photon crystals. These crystals generate an enormous energy (A-photon energy) as they reach the brink of decomposition. Even though this basic crystalline form does not exist naturally, the phenomenon of photon crystallization has been known to occur under certain extreme conditions, thus explaining the recent discovery of natural A-photon crystals.

An A-photon reactor is a device which takes photon particles through the process of collection, transformation (into A-photons), and extraction of energy from decomposition.

A-photon crystals come from the refinement of photon particles. When exposed to specific vibrations, refined A-photon crystals will begin to irradiate, initializing a chain-reaction decomposition. An A-photon reactor is a device which contains and governs this continual reaction. It can also increase the reaction efficiency through both positive and negative acceleration in vibrations, thus intensifying the energy discharged from crystal decomposition.

Modern science has only been able to make A-photon reactors fairly large in size. That is one reason their use is not as widespread as that of standard photon reactors.

In Phantasy Star Universe, there are no shields or types of armor to equip. Players are able to freely change their outfits without having to worry about the outfit's effect on their defensive power. So, exactly how does one improve their defense?

A layer of photons stretches over sections of the surface of all bodies. If something strikes at or collides with these photons, they will react in relation to the force of impact by collecting in the affected area, thus providing protection for the body. This is called the Shield Line System.

Shield lines can be changed, thus providing better protection and resistence to enemy attacks depending on which version you switch to. (SLS protection encompasses protection for fire, ice, electric, earth, light, dark, and general defense.)

Color	Elemental Resistance	Preview of Color Lines:
Blank	None
Red	Fire
Blue	Ice
Yellow	Electric
Orange	Earth
White	Light
Purple	Dark
Green	General

The primary trait of A-photon crystals is their ability to control space. This quality creates a distortion is space, allowing one to nanotrance, or store, weapons and other equipment in that distortion. A device which does this is known as a nanotrancer. These have become standard equipment for the Guardians.

This technology guarantees the convenience of space accomodation, even on an individual basis. Known as "a device that lets you say goodbye to your baggage," nanotrancers quickly spread in popularity across the Gurhal System. However, if the capacity of the spatial distortion is increased, the cost of a nanotrancer sky-rockets. That is why there is a fair amount of difference in efficiency between nanotrancers used by the general public and those of the Guardians and soldiers of the A.M.F.

Translations provided by EspioKaos. Guide compiled by Ryna.