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Inkay evolves when the DS is turned upside down, Pangoro evolves from Pancham when another Dark type is in the party.
Totally made up by me; something more redunant..Dive Battles, or changes to core battle systems such as the 1st type of a pokemon having regular stab weaknesses but the 2nd type has reduced stab/weaknesses, As a result some Pokemon has their typing swapped around such as Moltres and Charizard with the latter being Fire/Flying and the former being Flying/Fire to distance them from each over's shadow.
Possibly also the ability of adding 0.3-0.5x damage via passive status effects ala Magicka, such as dampening a foe with a water move makes them more susceptible to Grass/electric moves, or Oxidizing Steel (i know it can't rust) with a poisonous mist to make water hit a bit more.
