An allayer of fears.    From Wordnet, Princeton University. 

Verb (used with object), : to allay pain.    From Dictionary.com. 

I know this is an aside, but I really enjoyed the dog as companion and allayer of fear.    From Wordnik.com.  [Hauntings « Tales from the Reading Room] Reference

She became almost as much of a peacemaker, a smoother-down of rough interludes, an allayer of irritating ebullitions, as Dora was wont to be at home.    From Wordnik.com.  [A Houseful of Girls] Reference

In many of the same ways "The Cosby Show" did, it does double duty as both an allayer of white guilt ( "he's just like us") and an image makeover for black communities that resent their monolithic reputation for absentee fatherhood.    From Wordnik.com.  [FPOTUS: First Parents of the United States] Reference

Fortune in his private career, which threw such lustre on his path, that it rescued him from what must have been his inevitable fate, morbid cynicism: it was one of the happiest incidents that ever occurred to him: -- he formed the acquaintance of a man, seventeen years his senior -- who, in the lapse of a very short time, became to him a father and adviser, to whom present or absent he imparted every one of his schemes, thoughts, cares, sayings and doings; who was the unfailing allayer of his anxieties, alleviator of his sorrows, and most constant support of all his undertakings, -- Niccolo Niccoli, -- of whom I must take notice, as he was one of the most active stimulators of the forgery of the Annals.    From Wordnik.com.  [Tacitus and Bracciolini The Annals Forged in the XVth Century] Reference