Today in my English class I had a spell backfire and it acutally helped. The story is, that we were getting assigned presentations and I hate getting up in front of people and presenting. So I tried to do a simple spell that would change the teacher perception and not notice me, if that made sense. However the spell backfired and she did notice me, but instead of having to do a presentation in front of the entire class, I can just make send a presentation to my teacher. So maybe some spells backfire for a reason.
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