nightrider vs assaulter

nightrider and assaulter both are nouns.

Word	Noun	Adjective	Verb	Adverb
nightrider	Yes	No	No	No
assaulter	Yes	No	No	No

As nouns, assaulter is a hypernym of nightrider; that is, assaulter is a word with a broader meaning than nightrider:

nightrider: member of a secret mounted band in United States South after the American Civil War; committed acts of intimidation and revenge
assaulter: someone who attacks

Other hypernyms of nightrider include aggressor, assailant, attacker.

nightrider (noun)	assaulter (noun)
member of a secret mounted band in United States South after the American Civil War; committed acts of intimidation and revenge	someone who attacks