arch-fiend

demon, demonry, demonology; evil genius, fiend, familiar, daeva, devil; bad spirit, unclean spirit; cacodemon, incubus Eblis, shaitan, succubus and succuba; Frankenstein's monster; Titan, Shedim, Mephistopheles, Asmodeus, Moloch, Belial, Ahriman, fury, harpy; Friar Rush., vampire, ghoul; afreet, barghest, Loki; ogre, ogress; gnome, gin, jinn, imp, deev, lamia; bogie, bogle; nis, kobold, flibbertigibbet, fairy, brownie, pixy, elf, dwarf, urchin; Puck, Robin Goodfellow; leprechaun, Cluricaune, troll, dwerger, sprite, ouphe, bad fairy, nix, nixie, pigwidgeon, will-o'-the wisp., [Supernatural appearance] ghost, revenant, specter, apparition, spirit, shade, shadow, vision; hobglobin; wraith, spook, boggart, banshee, loup-garou, lemures; evil eye., merman, mermaid, merfolk; siren; satyr, faun; manito, manitou, manitu.

supernatural, weird, uncanny, unearthly, spectral; ghostly, ghost-like; elfin, elfish, elflike; fiendish, fiend-like; impish, demoniacal; haunted; pokerish [U.S.]

Satan, the Devil, Lucifer, Ahriman, Belial; Samael, Zamiel, Beelzebub, the Prince of the Devils., the tempter; the evil one, the evil spirit; the Adversary; the archenemy; the author of evil, the wicked one, the old Serpent; the Prince of darkness, the Prince of this world, the Prince of the power of the air; the foul fiend, the arch fiend; the devil incarnate; the common enemy, the angel of the bottomless pit; Abaddon, Apollyon., fallen angels, unclean spirits, devils; the rulers, the powers of darkness; inhabitants of Pandemonium; demon., diabolism; devilism, devilship; diabolology; satanism, manicheism; the cloven foot.

satanic, diabolic, devilish; infernal, hellborn.