8 25th Anniversary Celebrity Collaborator Cards are Unique Pokmon Cards with Star Power Copies: 3 Pokmon 25th Anniversary Celebrations Though the appeal of these cards may be very different from the rarest versions of the most iconic cards in major TCGs, there's no overestimating how rare they are
A foil Sliver Overlord is significantly more expensive than a non-foil Sliver Overlord
Since you assume your deck is sufficiently randomized, and that you run an average of 24 Pokmon, this means you have around an 8% chance of finding one of your Claydols first than any of your other Pokmon cards
So you're giving up more LP (unless it's really late-game and you somehow haven't died to a stray burn effect) for 350 more ATK and a probably not-very-significant amount of burn
Treacherous Greed Treacherous Greed is only good in token decks, I think, but it turns out that Orzhov is pretty good at that, and those decks also tend to like lifegain and life loss synergies
And the ones in black (and there are less than a dozen) tend to be 6-drops, the adventure side of Topaz Dragon notwithstanding