The Collaborative International Dictionary of English v.0.48:

Mediatory \Me"di*a*to*ry\, a.
   Mediatorial.
   [1913 Webster] Mediatress

WordNet (r) 3.0 (2006):

mediatory
    adj 1: of or related to or directed toward mediation

Moby Thesaurus II by Grady Ward, 1.0:

39 Moby Thesaurus words for "mediatory":
   Christlike, Christly, arbitrational, arbitrative, celestial,
   coming between, divine, empyrean, godlike, godly, going between,
   heavenly, incarnate, incarnated, intercessional, intercessive,
   intercessory, interlocutory, intermedial, intermediary,
   intermediate, intermediatory, intervening, interventional,
   made flesh, mediating, mediative, mediatorial, mesne, middle,
   pacificatory, propitiative, propitiatory, redemptive, salvational,
   self-existent, superhuman, supernatural, transcendent