Wiki founders automatically have bureaucrat rights in addition to administrator rights.
Other users may be granted the bureaucrat right through wiki adoption or by another bureaucrat on the wiki.
The only powers a bureaucrat has is to grant rollback, administrator and bureaucrat status to other users, and to take away administrator or rollback privileges. This can be done with the User Rights special page.
Only Wikia Staff can remove bureaucrat status from a user, usually at the request of the user, or, in the case of inactive users, at the request of the currently active community.