This is the answer.
My cat is 18, and she has become extraordinarily picky in the past year. The only thing she will eat reliably is Churu. She gets her medicine mixed in it twice a day, which means that now she wakes me up at 5 a.m. daily to beg for her breakfast.
This was my assumption. Or maybe witchcraft.
Ten-year-olds understand quite a lot of things. They don't always think before they act, but they would absolutely understand this object lesson.
It's water. It's not harmful. Getting splashed with water is most ten-year-olds' idea of a good time in most scenarios.
Is this the most constructive way to go about teaching a kid how to behave properly? No.
Is this going to scar the average kid for life? Also no.
According to the story, if your character dies in-game, by that point you're so addicted to the black magic that you ultimately can't go on living without it.