They take the money and vanish
Be careful not to overheat, as this can damage the card
When a new one is added, discard the old one and its effects
But the coolest DSK Collector Booster exclusives are probably the Japan Showcase, which is something that WotC launched with Duskmourn and described it as card art from Japanese artists and illustrators, a tribute to globally beloved and renowned art styles commonly found in Japanese hobby stores. They can come in traditional foil, or the very rare fracture foil (which also debuted in Duskmourn )
While these cards wont fill your gas tank, theyre still worth money on the secondary market
@pokemonrevolution recently presented a new and likely theory for these Grey Thick stamps, which I will quote here: Grey Stamp Theory Grey stamped 1st Edition Base set cards for the most part have commonly been considered to exist because of either A) The ink was low when they were stamped B) The stamp was not pressed down with enough force to create a nice dark color