"Phantasy Star (Japanese: ファンタシースター) is a series of console role-playing game video games and other supplementary media created by Sega. The original game debuted in 1987 on the Sega Master System with Phantasy Star, and continues into the present with Phantasy Star Universe, Sega's foray into the realm of MMORPGs. Each of the games in the series features a science fantasy setting featuring a cross-genre combination of magic and technology.
The series takes place in two similar fictional universes. While the first four games in the series are set in the planetary system of Algol, the later online games, Phantasy Star Online and Phantasy Star Universe, are set in other galaxies, with no canonical link to the original series, but rather only features the recurrence of common themes, enemies, and the primary antagonist, Dark Force."
Source: Wikipedia, "Phantasy_Star", available under the CC-BY-SA License.