netherworld vs imaginary place

netherworld and imaginary place both are nouns.

Word	Noun	Adjective	Verb	Adverb
netherworld	Yes	No	No	No
imaginary place	Yes	No	No	No

As nouns, imaginary place is a hypernym of netherworld; that is, imaginary place is a word with a broader meaning than netherworld:

netherworld: (religion) the world of the dead
imaginary place: a place that exists only in imagination; a place said to exist in fictional or religious writings

Other hypernyms of netherworld include fictitious place, mythical place.

netherworld (noun)	imaginary place (noun)
(religion) the world of the dead	a place that exists only in imagination; a place said to exist in fictional or religious writings