threaten vs peril

threaten is not a noun while peril is a noun.

Word	Noun	Adjective	Verb	Adverb
threaten	No	No	Yes	No
peril	Yes	No	Yes	No

As verbs, threaten and peril are synonyms defined as:

Other synonyms of threaten include endanger, imperil, jeopardise, jeopardize, menace.

threaten (noun)	peril (noun)
	a venture undertaken without regard to possible loss or injury
	a source of danger; a possibility of incurring loss or misfortune
	a state of danger involving risk

threaten (verb)	peril (verb)
to utter intentions of injury or punishment against	put in a dangerous, disadvantageous, or difficult position
to be a menacing indication of something	pose a threat to; present a danger to
pose a threat to; present a danger to