never vs ne'er

never and ne'er both are adverbs.

Word	Noun	Adjective	Verb	Adverb
never	No	No	No	Yes
ne'er	No	No	No	Yes

As adverbs, never and ne'er are synonyms defined as:

never and ne'er: not at all; certainly not; not in any circumstances; not ever; at no time in the past or future

never (adverb)	ne'er (adverb)
not at all; certainly not; not in any circumstances; not ever; at no time in the past or future	not at all; certainly not; not in any circumstances; not ever; at no time in the past or future