Abaddon  (a-bad ´on ).—The Hebrew name of an evil spirit or destroying angel called Apollyon in Greek. In mediæval literature he is regarded as the chief of the demons of the seventh hierarchy and the one who causes wars and uproars. Klopstock introduced him in his Messiah  under the name of Abbadona. He represents him as a fallen angel still bearing traces of his former dignity and repenting of his part in the rebellion against God. In Bunyan's Pilgrim's Progress  he meets and fights with Pilgrim.