Actually, Voldemort is not a "mudblood," he's a halfblood. (His mother was a witch and his father wasn't magical.) Though I do agree Harry Potter is one of the best series ever written.

My story's antagonists are kinda weird. I got one situation where the protagonist's best friend is targeted by the villain's closest assistant. Slightly later, she finds out there is a crown that can give her the power to defeat the antagonist's assistant. However, that crown was shattered over a thousand years ago by a curse.

Great, now I figured my plot out a bit more, and narrowed it down to one antagonist. Also, a tip for everybody. I forgot about this, it is so fundamental, but was recently reminded of it. Don't let the antagonist get drawn mercilessly into the plot. Have them make the choice to face the conflict, to get involved. A good example is Katniss, in The Hunger Games; Katniss's name isn't just drawn from a hat, her sister's name is pulled, and Katniss decides to take the place of her twelve-year-old sister in the Hunger Games.

(Sorry if I got it wrong, read it a long time ago, and sorry if I spoiled it for anyone.)