Drownyard Explorers

Four toughness is doing more here than the Clue is. Stapling investigate to an enters-the-battlefield trigger produces a defensive value brick: it walls off the early aggressive curve that blue often struggles against, eating smaller attackers and blocking profitably, then leaves behind a Clue that converts to a card later once the board has stabilized and the extra two mana is free to crack it. Investigate as a keyword priced card advantage as a deferred cost rather than an immediate one, which is what lets a creature like this be costed as a sturdy body now with the draw smeared across future turns. Toughness matters more than power because this thing holds ground rather than pushes it; four toughness survives the small clocks while the Clue sits in reserve as a draw step you buy on your own schedule. It is the plainest version of the soft card-advantage creature, asking nothing of your deckbuilding beyond room for an artifact token: no graveyard setup, no tribal payoff, just a wall that eventually replaces itself. Built without ambition and useful for exactly that reason, wherever a slow blue deck wants bodies that also dig.