Madame Hydra

The reward is keyed not to a color, a card type, or a keyword, but to a creature subtype shared across a whole faction of villains. Every Villain spell you cast while she is out spits out a menacing token, so the engine only turns over as fast as your deck commits to the tribe. The body is deliberately modest (a 2/3 that accomplishes nothing in combat alone), because the value is meant to accrue off the board around her rather than in the card itself. Menace on the tokens is the detail that keeps them from being chump-fodder: a widening board of evasive attackers forces opponents to hold back multiple blockers, converting a go-wide plan into a real clock. The design belongs to the "cast a thing of type X, get a body" school that Young Pyromancer popularized, but pinned to a named tribe rather than a spell type, which shifts the deckbuilding constraint from what you cast to who you cast. The catch worth internalizing is that she taxes herself out of her own engine: resolving her produces nothing, since the trigger only reads spells cast after she is already in play. Load the deck with Villains and each subsequent cast does double duty; build thin and she is a 2/3 that occasionally coughs up a token. The tribe is the cost, and the tribe is the payoff.