Ceres was one of the first planet colonies of humanity, perhaps during the Little Diaspora.

When a planetoid struck Terra in 13402 BG, Ceres became the new capital of the Imperial Seat.

From Ceres the Empire expanded and became the Empire of Ten Worlds and then the Empire of a Thousand Worlds

However a rebellion erupted and Ceres was destroyed in 11105 BG. Thus begun the Age of Pretenders

Behind the scenes

Ceres probably is meant to be the real-life dwarf planet Ceres.