pokemon card value guide Pokémon Rarity (Credits to "Sleeve No Behind") : r/PokemonTCG Price Guide from 2004 :

[c]Yorion, Sky Nomad[/c] sees competitive play in a multitude of formats, in part due to its more forgiving deckbuilding restriction

So every 10 stamps, you get a $5 reward

For example, in the Black and White games, only Pokemon indigenous to the Unova region were catchable, so in the first Black and White TCG expansion, only Unova Pokemon were included

While Imps Mischief is in some ways better, because it gives a Deflecting Swat effect to Black, its also nearly $30, and not worth it unless youre playing at the highest power levels in which case youre probably playing red and/or blue anyways, defeating the purpose