umpire (n.)
arbitrator, mediator, adjudicator
1H6 II.v.29 [Mortimer to Gaolers] Just Death, kind umpire of men's miseries
MW I.i.129 [Evans to all] There is three umpires in this matter
RJ IV.i.63 [Juliet to Friar] 'Twixt my extremes and me this bloody knife / Shall play the umpire
TNK I.iii.45 [Hippolyta to Emilia] Theseus cannot be umpire to himself