Benthic Criminologists

The card advantage here is fenced behind a resource most blue decks don't naturally accumulate: artifacts to feed it. That's the tension worth reading. The 4/5 body is a genuine blocker and a slow clock, but every draw rides on a sacrifice trigger that fires on entry and on every attack, and Benthic Criminologists cannot pay that cost with itself: it's a Merfolk, not an artifact. Drop it into a deck with nothing to feed it and the payload never fires at all. The optional sacrifice is what keeps this honest rather than punishing: with no artifacts around, the ability simply idles and you still have a five-mana beater. Fill the deck with Treasure, Clues, or cheap disposable equipment and each swing converts a chunk of nothing into a card, turning the trigger into a repeatable engine while the body keeps applying pressure. That framing puts it in a long line of blue value creatures built to reward a support structure rather than stand alone, closer in spirit to artifact-sacrifice payoffs than to a stock card-draw finisher. The design honesty is that the printed line hands you nothing on its own: the body is a fair rate, and every card past that is earned entirely by the artifact supply you construct around it, not by the creature entering play.