amphisbaena vs mythical monster

amphisbaena and mythical monster both are nouns.

Word	Noun	Adjective	Verb	Adverb
amphisbaena	Yes	No	No	No
mythical monster	Yes	No	No	No

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

amphisbaena: (classical mythology) a serpent with a head at each end of its body
mythical monster: a monster renowned in folklore and myth

Other hypernyms of amphisbaena include mythical creature.

amphisbaena (noun)	mythical monster (noun)
(classical mythology) a serpent with a head at each end of its body	a monster renowned in folklore and myth