Understanding Pokemon Card Rarity symbols can be complicated, not only because Nintendo have never seemed to explain it efficiently, but because theres a handful of symbols to understand and it can get confusing
Keep in mind that Gold Star Espeon/Umbreon PSA 10s very rarely hit the open market these days, so barring a market crash, you will gain far more the longer you hold on to that (but if you need the cash or have other collecting goals then its definitely a great time to sell)
Doing this while adding loyalty to Dack is even better
Therefore, cards that prevent the opponent from Setting or flipping (like "Dark Simorgh", "Searchlightman", and "Light of Intervention"), or cards that prevent your cards from being flipped down, are effective
You can only activate 1 "Ledger of Legerdemain" per turn
Before purchasing, browse for similar items to compare prices and ensure you get the best deal