Cerberus vs mythical creature

Cerberus and mythical creature both are nouns.

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

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

Cerberus: (Greek mythology) the three-headed dog guarding the entrance to Hades; son of Typhon
mythical creature: a monster renowned in folklore and myth

Other hypernyms of Cerberus include mythical monster.

Cerberus (noun)	mythical creature (noun)
(Greek mythology) the three-headed dog guarding the entrance to Hades; son of Typhon	a monster renowned in folklore and myth