[Ah, fun light conversation.]

. . . they arrived on an ocean planet, created land on it, and started a war with the native people. In the end, the natives--the Radiant--took control of the ship, and their leader sacrificed herself to destroy much of the land that had been created. Humanity refers to that event as the Cataclysm. It took a lot of lives.

Thousands of years have passed since then. The Legacy was lost for many of them.