Whenever a non-Stone card is added to your deck, create a Stone copy of the added card
Notes: Hologram stonks 📈📈📈
Okay, but in all seriousness, I feel like this makes for interesting synergy with Stone Cards and other deckfixing builds. The fact that the source card has to be non-Stone means you can't just spam only Stone (and also implementing it that way prevents infinite loops). Since the cards are copies, they would keep their rank and suit underneath the stone, so you could use Tarot cards or Vampire to revert their enhancement so you can use them normally. Like I said, it might be a bit strong with Hologram, but it's also a specific Uncommon-Rare combination, and I feel like the balance issue is mostly with Hologram. What do you think?