Mega Stones cannot be taken via Thief, Covet, Trick, or Switcheroo. Trainers on the same team during a Multi Battle will each be able to Mega Evolve once during the battle. If a Mega Evolved Pokémon faints, but is later revived, that Pokémon cannot obtain a Mega Evolved state again for the remaining duration of the battle. A Mega Evolved Pokémon can only revert back to its original state upon fainting or the conclusion of the battle. Switching the Mega Evolved Pokémon out will not dissolve a Mega Evolution. Once per battle, only a single Pokémon for each Trainer may Mega Evolve.
In order to Mega Evolve, the Pokémon must be holding the appropriate Mega Stones (with the exception of Rayquaza which is only required to know the move Dragon Ascent).
