It is a reference to Magic The Gathering. Blue decks are known for wildly changing the rules of the game. Black decks are known for interacting with death and the graveyard which is where cards go after they are used.
A paraphrasing of the GP without using magic terminology is to say that they are playing by the rules in an unexpected way using unexpected combinations and sequences. More briefly "playing by the rules as written".
What does this sentence even mean?
It is a reference to Magic The Gathering. Blue decks are known for wildly changing the rules of the game. Black decks are known for interacting with death and the graveyard which is where cards go after they are used.
A paraphrasing of the GP without using magic terminology is to say that they are playing by the rules in an unexpected way using unexpected combinations and sequences. More briefly "playing by the rules as written".