pyromancer vs diviner

pyromancer and diviner both are nouns.

Word	Noun	Adjective	Verb	Adverb
pyromancer	Yes	No	No	No
diviner	Yes	No	No	No

As nouns, diviner is a hypernym of pyromancer; that is, diviner is a word with a broader meaning than pyromancer:

pyromancer: one who practices pyromancy
diviner: someone who claims to discover hidden knowledge with the aid of supernatural powers

pyromancer (noun)	diviner (noun)
one who practices pyromancy	someone who claims to discover hidden knowledge with the aid of supernatural powers