The Shield of Geba was the Emperor's personal guard, established during the Era of Absolute Expansion as the elite protection detail for the imperial family and high-value assets. Its operatives were selected for loyalty and discretion above all else. Their function was to ensure that no assassination, internal threat, or external force ever reached the people they guarded.
After the Fracture, the Shield protected royals during the escapes and civil wars that followed Emperor Auren's assassination. When the visible empire collapsed and the Shadow Rulers emerged from the Emperor's Shadow, the Shield's descendants became the only people who ever see the Shadow Rulers' faces. They serve as their guards in hidden networks, the last unbroken line between the original imperial household and the covert governance that replaced it.
During the Warlord Eras they operated covertly to protect hidden rulers from rogue factions. In the modern era no formal unit exists. They continue as unseen protectors in the Underworld, the hereditary guardians of a government the planet does not believe is real.