Adeptus Custodes

These are among the mightiest warriors in all the Imperium, the praetorians of the Emperor. They stand ever-vigilant outside the brazen doors which seal His holy chamber. They are entirely beyond reproach and they are among the few over whom the Inquisition has no power.
They never leave the inner sanctums of the Imperial Palace and serve from birth to death within its hallowed halls. Yet they are among the few of the servants of mankind who will ever look upon the Emperor directly, and for that they receive blessings beyond all measure.