reliever

noun

1

a pitcher who does not start the game

Synonym: relief pitcher fireman

2

a person who reduces the intensity (e.g., of fears) and calms and pacifies

a reliever of anxiety

an allayer of fears

Synonym: allayer comforter

3

someone who takes the place of another (as when things get dangerous or difficult)

the star had a stand-in for dangerous scenes

we need extra employees for summer fill-ins

Synonym: stand-in substitute relief backup backup man fill-in