As told before, the Crimson Mages were undying who looked like humans. It wasn't hard for them to blend in with the crowd and live a normal life. Unless a special method was used, they couldn't be differentiated from normal humans.
Still, that didn't mean they could move freely in the empire, as the strongest man, in order to deal with them, created a special department right after becoming an emperor.
It was called WK. The ones who hunted them down were called knight-errant, aka wandering knights.
They had two jobs. The first was, of course, hunting down the crimson mages that had snuck into the empire and eradicating people who had accepted Chaos before they could cause mayhem. The second was to accept a student every three years and pass on to them their teaching, train them until they become so capable that they are able to track down crimson mages, differentiate them and Chaotic beings from the masses, and hunt them down.
