I wonder if this is a question of the moth attracting the flame, rather than the other way around?
That is to say, perhaps this boy was already courting the occult and the certain images fron M:TG resonated with him, rather than the images causing an interest in the occult.
I used to observe this while I was teaching middle schoolers: the ones who were already depressed began gravitating to the “emo music” (I sound like an old lady when I put that in quotes

). The music didn’t make them that way, they were already there, and found the music an adequate outlet for expression.
On the other hand, if
I listen to emo music, it DOES depress me.
The point is, what was this boy like before he started playing M:TG? Maybe his interest in the occult predates it.
Cheers,
C
p.s. My husband and I used to play ALL THE TIME in the 90s. And I wholeheartedly agree with previous posters who bemoan the wasted resources the game encourages. Anyone want to buy our collection? Maybe recoup some of our losses?