Not a problem. I'm just doing my best not to spoil anything regarding Unlimited Blade Works, (because it is the best path). I'm not clear on how the cleansing of the grail works either, as I did not read Fate/Hallow, but I'm just brainstorming right now. What I do know is that someone did something they shouldn't have, and the grail was corrupted by negative emotions or something. Originally the grail could not summon "evil" heroes, but now it can. Which goes along with the idea that [@Constantine] had.

Magic has the benefit of being magic, so the how is not so important, or at least we don't have to worry about that for now. If you need clarification on anything in the future just ask me. That doesn't mean that everything needs to be right mind you, I just want to have fun. :)