Ethereal Investigator

The scaling is written into the entrance: the enters-the-battlefield trigger investigates once per opponent, so at a crowded table it arrives with a fistful of Clues rather than the single token you'd get in a duel. But that pile of Clues isn't the payoff by itself; it's the fuel for a once-per-turn engine. Because cracking a Clue is a draw, the Clue you sacrifice on a turn where you've already drawn once flips the second-draw clause and spins off a 1/1 white flyer. Crucially, that trigger fires exactly once per turn: the third and fourth Clues you crack that same turn refill your hand but make no further Spirits. That timing is the whole discipline of the card. The Clues want to be hoarded for raw card advantage; the token-maker wants you to time one draw precisely, every turn, on top of a first draw you were making anyway. Squeezing both out of the same resource is the puzzle. It rewards a deck that draws in a steady drip rather than one enormous burst, since a single overloaded turn converts to one Spirit no matter how many cards you rip. It sits in a line of blue investigate payoffs that treat the Clue less as an emergency card-draw valve and more as a metered resource, and the more opponents seated across from you, the deeper the reserve the front half hands over to meter out.