This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
魖 combines the ghost radical 鬼 with 虚, which likely contributes a phonetic element. The exact historical development is uncertain.
A ghost (鬼) inside an empty void (虚) suggests something eerie and insubstantial, but its exact meaning is unclear.
For キョ, imagine a ghostly 'kyo' sound echoing from the void: kyo -> キョ.