I'm looking for a word to describe a role or an office or something like that, which is filled by one person at once, but that person can change. Sort of "moniker" but in reverse. Think "James Bond" or Doctor Who", where the identity continues, even though the actual individuals change. When we say "The King is dead. Long Live the King", that's the idea - we can ask "Who is the King?", or we can say "He is Maclean of Maclean".
If Bruce Wayne got too old and stiff to be Batman any more, he'd pass his ___ [what?] to his protege.
I've thought of "Title" or Crown", but title has too many other meanings to be useful to me (and is "James Bond" a title anyway?). But its not a "Role" either - being King isn't a role!
So, I'm looking for a word which encapsulates this idea of transferable identity.