Talk:Light Generation/@comment-4013211-20110522082027/@comment-29325824-20180927175028

^Don't want to be that guy, but the spell is "Expecto Patronum".

Anyway, you're kinda right. While Dementors do seem to prefer dark places, it's not the light itself but the pure positive emotions in the spell that repels them. However, Dementors aren't scared of the Patronus, it's just that their despair powers have no effect at all on an embodiment of pure positivity.