If you use Klefki STS’s ability and attacches itself to an Yveltal BKT, is the Yveltal BKT immune to Megas? Or does Fright Night shut the Klefki effect off?
Yes, because Klefki becomes a Tool
What do you mean yes? There are two options. Klefki becomes a tool, making it useless on yveltal bkt against megas.
You could klefki to the fright night and then stream hex maniac.