sardaukar
A fictional organization of elite warriors from the DUNE series.
They are completely loyal to Emperor Shaddam IV, ruler of the known universe.
The Sardaukar are a penal army secretly trained on the inhospitable Imperial prison planet Salusa Secundus, and the harsh conditions there ensure that only the strongest and most "ferocious" men survive. The weaker ones are sacrified during training and their blood used in bloody rituals to ensure their loyalty to the Emperor.
Sardaukar training emphasizes ruthlessness, near-suicidal disregard for personal safety, and the use of cruelty as a standard psy-ops weapon in order to weaken opponents with terror. Their uniforms are described as gray with silver and gold trim.