This is a digital file format used by the Nintendo Switch for games and DLC.

Refers to The Hidden Treasure of Area Zero , a two-part expansion including The Teal Mask and The Indigo Disk . Why the DLC Makes the Game "Better"

The expansion brings back over 230 familiar Pokémon that were not in the base game.

The Indigo Disk introduces higher-level double battles and strategic matches that many players find more engaging than the base game's main story.