Powder goes away the turn it's used?The problem with Powder is that it only lasts a single turn... so if you opponent does anything OTHER than attack with a Fire-type move, you just wasted your turn. With Vivillion's defenses, that means you are either KO'd or getting set up on. Not too useful, but a fun gimmick.
If it does get distributed to Ferrothorn or Forretress, however, now THAT will be hilarious. Talk about mind games!
Oh, I just assumed the "powder" stays on the target till it uses a fire type move, then boom. It would have been nice to block the use of fire type moves.