Syr Elenora, the Discerning

The tax and the payoff pull in the same direction, which is the quiet cleverness here. A creature whose power scales with cards in hand normally invites the obvious answer: kill it before you have to spend cards protecting it. But the target-tax clause makes that math ugly, since any spell an opponent casts at her costs two more, and the same full grip that makes her big is the grip you would rather not empty defending her. She rewards holding cards and punishes the interaction that would otherwise punish holding cards. The enter-the-battlefield draw is the tell: it refills you by one on arrival, nudging her power up a point and immediately widening the gap she has to be answered through. The four toughness is doing load-bearing work too, since a variable-power body with a fixed, respectable rear end is much harder to burn out than to outrace. Note the seam in the tax, though: it catches only opponents' spells, so activated and triggered abilities that target her (edicts aside, an Icy-style tap, a pinger's damage) walk right past the surcharge. This is control's payoff creature done as a puzzle rather than a bomb: no evasion, no protection from a board wipe, just a threat that gets harder to remove the more the game state favors the deck already built to sit behind counterspells and card draw. The ceiling is real but conditional, and the floor is honest: cast her as your last card and her own draw leaves you at one, a 1/4 that still taxed the first spell aimed at it.