Harpy vs mythical creature

Harpy and mythical creature both are nouns.

Word	Noun	Adjective	Verb	Adverb
Harpy	Yes	No	No	No
mythical creature	Yes	No	No	No

As nouns, mythical creature is a hypernym of Harpy; that is, mythical creature is a word with a broader meaning than Harpy:

Harpy: (Greek mythology) vicious winged monster; often depicted as a bird with the head of a woman
mythical creature: a monster renowned in folklore and myth

Other hypernyms of Harpy include mythical monster.

Harpy (noun)	mythical creature (noun)
(Greek mythology) vicious winged monster; often depicted as a bird with the head of a woman	a monster renowned in folklore and myth