The Royal Guard serve the Emperor of the Centauri Republic in many different ways, acting in any role from bodyguard to elite trooper on the front lines of battle to an expedient assassination in the dark if such is the Emperors will.
The Vorlons have thus become more myth than reality in the eyes of many races and many wild stories are told about them. There are tales of fantastic cities of unbelievable technology on their worlds and living ships miles across. It is even said that anyone seeing a Vorlon will be instantly turned to stone.