Phantasy Star IV: The End of the Millennium

Phantasy Star IV takes place 1,000 years after the events of Phantasy Star II and 1,000 years before the era of Phantasy Star III . After an event called the Great Collapse, much of the once-thriving planet Motavia has reverted to its original desert-state as the climate and biosphere-controlling devices installed over a thousand years previously begin to fail, and life has become progressively more difficult for the planet's inhabitants. To make matters worse, there has been a marked increase in the numbers of the "biomonsters", a catch-all term for the strange and violent aberrations of Motavia's flora and fauna. " Hired by Piata Academy on Motavia, hunters Alys Brangwin and her young partner Chaz Ashley begin their investigation into the relationship between the biomonster problem and the planet's ecological crisis.

Joined by others along the way, they connect the world's troubles to a cult leader called Zio, "The Black Magician", whose aims appear to be total annihilation of not only Motavia but of the whole Algol solar system . During their initial confrontation, Zio summons Dark Force and mortally wounds Alys with its Dark Energy Wave. Taking the lead upon her passing, Chaz is joined by Alys's wizard acquaintance Rune Walsh who helps break the barrier on Zio's tower and eliminate the wizard to restore the computer systems maintaining Motavia. With no change in Algo's abnormal conditions, the party turns their attention to a malfunctioning satellite space station found to be contaminated by Dark Force, which they are forced to engage and purge.

However, Algo's disasters remain unabated and the party is further baffled as they encounter multiple incarnations of Dark Force along the way. Traveling to Rykros, an unknown fourth planet of the Algo solar system, Chaz and his companions learn of the Profound Darkness: a powerful entity banished behind a planetary seal billions of years ago that is able to manifest its hatred in physical form as Dark Force every thousand years due to fluctuations in the seal. With the seal now severely weakened by the planet Parma's destruction during the Great Collapse, Chaz and his party enter the Profound Darkness's dimension and eliminate it before it is able to break completely free and destroy the galaxy. With the evil banished for good and the party going their separate ways, Rika – a numan girl in the group – chooses to stay behind with Chaz as they bid everyone farewell, remembering the sacrifice of those who have defended Algo through the ages and awaiting the next one to come.