Most legitimate shops can guarantee authenticity, as there are many fake cards in the Pokemon trading world
In Modern, you want to play this effect at Instant speed even if you have to settle for +3/+3 in that other format
But bonus sheet cards are supposed to be a glittering incentive to dive harder into a set, cracking more packs or buying the punishingly expensive collector boosters in exchange for unique, rethemed versions of existing, widely playable cards for your decks
But with its effect, Borrelsword Dragon can literally destroy any monster in battle no matter the other monsters attack
The playmat is still exclusive to the winner, and the art suits the wide space really well
If you have any means to repeat this trigger, flicker, or bounce Black Cat, you're on the road to the best side of card advantage, while your poor opponent gets severely reduced card selection