I like to think of Illyana as being herself, but as 'Art', I knew Claremont sort of took elements of Dante's 'Inferno' and Moorcock's 'Elric' as inspiration for Magik, plus a bit of Larry Niven ("Stepping Disks") and Lovecraft ("Elder Gods")
I felt a bit overwhelmed last year, though, when I saw how profoundly "Heavy Metal's" core story about the Loc-Nar, the young girl, and Taarna mirrors Illyana. It seems undeniable to me, comparing this clip from the movie of a one-handed devil horned demon with a medalion necklace fighting a warrioress/little girl with armor on one arm, and a magic sword that vanquishes the source of all evil.
The primary song of the "Taarna" arc is "Veteran of the Psychic Wars", performed by Blue Oyster Cult, lyrics by Michael Moorcock, of Elric & "Stormbringer", the infamous soul-eating sword.
Heavy Metal premiered August 1981, UXM#160 was August 1982, with Belasco having already been introduced in Ka-Zar#11 in February 1982.
So I believe the overlap of "Heavy Metal Devil Music" with Magik is essentially undeniable. Even if Claremont is unaware of the influence, if he watched Heavy Metal before X-Men #160 was finished, the inspiration is there to see.
https://youtu.be/8erRew5Jbg0