One for Sorrow

Oh yes, I don't think Harry had any way of actually knowing what it would do--he's never seen a spell like that any more than Draco has. (Well, he saw Snape in the pensieve but it's not in his head.) I just tend to think it's kind of okay, you didn't know what it would do, but unfortunately once it happens you can certainly see how it fits "for enemies." Actually, I'm wondering how Harry would sound being grilled over just what he thought it would do, because what works in the scene is that he isn't thinking, he's just instinctively reaching for it instead of expelliarimus or anything else.