It focuses on sifting through your deck to get the cards you need whilst healing or buffing your characters, for example
Judge Magister Gabranth is a fairly bad card to draw much later in the game, but establishing it early is extremely threatening
Its a nice win condition for Aetherworks Marvel decks that can help dig to find the card as well as cast the first copy, which doesnt need to be cast from hand
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So as long as development tested the Rats in high numbers to make sure it wasn't degenerate, we knew it was safe to break the rule (well, as safe as development can ever be the real world just has so many more playtesters.) Rule #4 Breaking Rules Is A Test For the Future When we do choose to break a rule, R&D tends to keep an eye on the card
They are much rarer than other card types, and they don't always make appearances in games, and they change the fundamentals of the game slightly when in play