Which new type did Pokémon X and Y add to the Pokémon battle system?

Pokémon X and Y added the Fairy type to the Pokémon battle system. It was the first new type introduced since Pokémon Gold and Silver added the Dark and Steel types in 1999.

Fairy-type Pokémon and moves were designed partly to rebalance the battle system. Fairy is especially effective against Dragon-type Pokémon, while Fairy Pokémon are weak to Poison and Steel attacks. This gave established species and moves new strategic roles.

The type also changed the classifications of some older Pokémon. For example, several Pokémon that had previously been pure or dual types received Fairy as a new type in X and Y. The change affected both competitive battling and the way players understood familiar Pokémon.

Fairy is sometimes mistaken for an anime-only concept or a temporary battle mechanic. It is a permanent Pokémon type used across the games and other franchise media. X and Y introduced it alongside other major features such as Mega Evolution and fully polygonal graphics.