Definition of archfiend in English:

archfiend

noun

literary
  • A chief fiend, especially the Devil.

    • ‘The background makes it fun to pick your favorite archfiends, and easy to work up a ‘reason’ for the battle… I like the idea of exploring the politics of Hell.’
    • ‘We are going to that castle over there, and striking a deal with the resident archfiend to make sure that they don't escape.’
    • ‘Bands of angels and archangels follow the divine leader, while troops of demons and archfiends hasten after the evil lord.’

Pronunciation:

archfiend

/ˌärCHˈfēnd/