What was the first downloadable expansion released for a Pokémon main-series game?
Answer
The Isle of Armor
The Isle of Armor was the first downloadable expansion released for a Pokémon main-series game.
It was the first part of the Pokémon Sword and Shield Expansion Pass, released in June 2020 for Nintendo Switch. The expansion added a new island area, new story content, returning Pokémon, regional forms, and the Legendary Pokémon Kubfu, which can evolve into Urshifu.
The second Sword and Shield expansion, The Crown Tundra, followed in October 2020. Together, the two expansions replaced the older pattern in which Pokémon games received a separate enhanced edition, such as Crystal, Emerald, or Platinum.
The Isle of Armor is sometimes confused with The Crown Tundra because both formed the same Expansion Pass. It is also separate from The Hidden Treasure of Area Zero, the two-part downloadable content package for Pokémon Scarlet and Violet released later.