Mewtwo @ Rocky Helmet / Leftovers Trait: Prankster Modest Nature (+SAtk, -Atk) - Stored Power - Aura Sphere - Taunt - Substitute This is THE Baton Pass receiver. Sit back and watch how you destroy everything with Stored Power after obtaining +6 in every stat. Aura Sphere is obviously necessary to hit the occasional Dark types. The real selling point of this set though is that Unaware/Prankster Heart Swap users cannot stop it. Thanks to Prankster Taunt, Mewtwo can block any attempts by the opponent to steal its boosts before they have the chance. Although the rise in Sp. Attack is ignored by Unaware users, Stored Power still maintains the same BP as if the boosted were applied. Although you'll likely be passing this Mewtwo a sub in order to keep Blissey away, the move Substitute allows you to set up another one in case your sub broke for whatever reason. Rocky Helmet is the preferred item as it gives Mewtwo a pinch way of beating Shedinja, although Leftovers could also be used to stay healthy in sandstorm/hail.