cockatrice vs mythical creature

cockatrice and mythical creature both are nouns.

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

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

cockatrice: monster hatched by a reptile from a cock's egg; able to kill with a glance
mythical creature: a monster renowned in folklore and myth

Other hypernyms of cockatrice include mythical monster.

cockatrice (noun)	mythical creature (noun)
monster hatched by a reptile from a cock's egg; able to kill with a glance	a monster renowned in folklore and myth