The 1st Imperial Legion, who fill the role of these chaps…
Household Division - Wikipedia
…and other nations’ equivalents of those who guard the head of state and perform ceremonial duties, while also being surpassingly lethal.
(Not the equivalent of the Secret Service: that’s the Sovereign Protectors. But they would be the equivalent of the marines who stand on guard at the White House.)
((Unlike the King’s Guard, however, the Imperial Guard will arrest and quite possibly shoot sufficiently idiotic tourists. The Imperial Palace, after all, is a working palace, and has a dungeon more than adequate to teach people the error of their ways.))