A Prime Archator is a person who is at the top of a government, especially a national government.
This includes presidents, prime ministers, kings and queens, tsars, or any other such positions which rely on the belief in political "authority".
These are the people who instruct others to archate on behalf of the State.
I suppose you could have minor Prime Archators, too. Mayors, police chiefs, and the head of other gangs which live by archation could be Prime Archators in their limited realm.
It's bad enough to be an archator. It's orders of magnitude worse to be a Prime Archator.