The Blue Sea Star is a celestial body of unknown composition visible in the skies above Fódlan between the months of the Blue Sea Moon and the Ethereal Moon.
The Blue Sea Star is believed by followers of the Church of Seiros to be the home of the Goddess, and the place from which Saint Seiros descended to bring salvation to Fódlan 41 years before the founding of the Adrestian Empire. When it reappears in the skies during the Blue Sea Moon, the Goddess's rebirth is celebrated, and when it departs during the Ethereal Moon, it is said that the Goddess prays for peace in the world.
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Records and accounts forbidden by the Church indicate that in ancient times, Sothis traveled to Fódlan from a faraway place, often theorized to be the Blue Sea Star. She took on a human form and used her divine blood to create her children, Seiros and the Nabatean people, who coexisted with the land's native humans until the rise of Agartha's fatal arrogance.