1) Deputy 2) Surrogate 
Vicegerent is the official administrative deputy of a ruler or head of state: vice (in place of) + gerere (to carry on, conduct). ==Notable vicegerents== ...
acting in place of another; having delegated authority
• (a.) Having or exercising delegated power; acting by substitution, or in the place of another. • (n.) An officer who is deputed by a superior, or by proper authority, to exercise the powers of another; a lieutenant; a vicar. • (a.) Having or exercising delegated power; acting by substitution, or in the place of another.Vicegerent: ...
Vice·ge'rent adjective [ Vice , adjective + gerent : confer French vicegérant .] Having or exercising delegated power; acting by substitution, or in the place of another. Milton. 
[n] - someone appointed by a ruler as an administrative deputy
noun someone appointed by a ruler as an administrative deputy