Sega released Phantasy Star II for the Mega Drive in 1989, with the Genesis version arriving in North America the same year. Set about a thousand years after the first game, the Algol star system is managed by Mother Brain, a vast computer that controls the climate and supplies of the colonies. When the system starts to malfunction and monsters appear, government agent Rolf is sent to investigate, joined by Nei, a young woman who is half human and half animal. Along the way, up to eight characters can join the party, each with their own techniques and equipment. The science-fiction story was unusually dark and ambitious for its time, and one of its major events is still remembered as a shocking moment in console RPG history. Battles are shown from behind the party, with enemies animated in detail, and the large dungeons demand careful exploration. It is considered a milestone among 16-bit role-playing games.