From the Phantom Regiment website:
Set amidst a musical landscape of sweeping, symphonic scores and dark new musical textures, Phantasm explores the stark contrasts between reality and imagination, the real and the unreal. A twisted musical and visual challenger emerges as an intruder from within the classical tradition of the Phantom Regiment. This seductive, powerful character begins life solely as an invasion of mind, but quickly becomes something more, blurring the lines between beauty, madness, and desire. Forced to confront the enemy within, newfound strength leads to an awakening, and phantasy gives way to reality…
Additional description:
ACT 1: Dark forces are in control of the corps, changing their normal white to black. It affects everything from their persona to the music. This act contains some of the most frenetic field movement and guard work. It is meant to make us feel unbalanced and confused, as is the corps in their struggle against the dark force.
ACT 2: The corps fights to regain who they are. You will notice a lot of struggle for control over the dark forces, resulting in the appearance of the light force as the Rachmaninov begins. You will note that the music moves from dark, atonal at times (quite unlike what we associate with Regiment), to a beautiful ballad in a major key.
ACT 3: The corps begins to win control as the battle rages, with the corps finally breaking the "spell," reflected in the white helmets, white guard units, and the bright flag design. Even the music reflects the beautiful, romantic/classical genre PR is known for.
These are descriptions that were shared by someone else; they are not my personal interpretations.