@woody
Should have scanned for willpower.. but if you can't find harry explaining dark magic somewhere in 17 books...
And feeling not emotion?!? That does not compute... Feelings are emotional, that feeling of power would be considered things like pride, gloating, smugness, that heady sense if purpose before the kill, ect. Plenty of adjectives to apply to it. But if you wanna break it down, it creates euphoria and happiness, if you need an emotion that's recognizable to you.