Lost City (Lost Origin 161/196)

Lost City

Whenever a Pokémon (either yours or your opponent's) is Knocked Out, put that Pokémon in the Lost Zone instead of the discard pile. (Discard all attached cards.)

Card rule

This Stadium stays in play when you play it. Discard it if another Stadium comes into play. If a Stadium with the same name is in play, you can't play this card.