Geryon vs mythical creature

Geryon and mythical creature both are nouns.

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

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

Geryon: (Greek mythology) a mythical monster with three heads that was slain by Hercules
mythical creature: a monster renowned in folklore and myth

Other hypernyms of Geryon include mythical monster.

Geryon (noun)	mythical creature (noun)
(Greek mythology) a mythical monster with three heads that was slain by Hercules	a monster renowned in folklore and myth