The Dark type was introduced alongside the Steel type in Pokémon’s second generation.
Both types debuted in Pokémon Gold and Silver, which were first released in Japan in 1999. Their addition expanded the battle system beyond the original 15 types and helped rebalance matchups between existing Pokémon.
Dark-type Pokémon were designed to represent moves and creatures associated with trickery, malice, or nighttime themes. Steel-type Pokémon emphasized metallic bodies, armor, and durability. The two types also interacted with the original type chart in new ways.
The Fairy type is a much later addition, debuting in the sixth generation with Pokémon X and Y. That timing makes Fairy a frequent mix-up when players remember that new types were added to the series.