intercessor
/ˈɪntə(ɹ)ˌsɛsə(ɹ)/noun
University
1
A person who intercedes; a mediator; one who reconciles enemies, or pleads for another.
2
Especially: a heavenly saint who intercedes (with God) on behalf of a mere mortal.
3
A middleman, intermediary
4
A bishop who acts during a vacancy in a see.