The Scarlet Witch

Cost reduction that scales with a creature's power is a rare pairing, and the shape here inverts the usual math of big-spell decks. Most cost reducers shave a flat amount or key off card count; this one keys off a variable, the power of a single body, which means the discount only matters as much as you can push that number. A static 2/3 gives you a floor of two off, already a fair engine, but the whole design begs for red's temporary and permanent pump effects to turn a marginal trim into a genuine bargain: a single power boost is worth exactly one mana on every qualifying spell you cast that turn. The mana value 4-or-greater clause is the restriction that pays for it, walling off the trivial abuse. No free cantrips, no chaining out one-mana burn for value; the reduction is reserved for the expensive instants and sorceries where a discount actually swings a game, the X-spells and the top-end finishers. Three toughness is what keeps her out of range of the incidental pings that clean up mana dorks, so she survives to hold the discount live across multiple turns. She is a stationary enabler by nature: the ability runs whether she attacks or sits back, which frees the deck to treat her as pure cost structure and spend its turns casting the spells she cheapens rather than protecting a body that has to swing.