Tetsuo, Imperial Champion

The design hinges on a single number doing double duty: the greatest mana value among the Equipment strapped to this 3/3 becomes both a damage figure and a free-cast ceiling. Equipment mana value normally functions as a cost you pay once and forget; here it becomes a live dial you read off the battlefield at attack time. Attach nothing and the trigger never fires, which is the discipline that keeps the payout in check: you have to invest in the arsenal before the champion cashes in. The sharper half is the second mode. Most "cast a spell for free" effects hardcode the mana value cap in their own text; this one takes its ceiling from whatever heavy steel is currently attached, so bolting on a pricier weapon raises the bar for the instants and sorceries you can fire off. And because it triggers during the declare-attackers step, that free cast lands at instant speed, which matters most for the spells that want an empty stack: a removal spell to clear a would-be blocker before blocks, a burn spell to the face alongside the swing, a cantrip to refuel mid-combat. The choice between reach and a free cast makes every attack a fork: aim the number at a face or a blocker, or spend it launching a spell you would otherwise have to pay for. The Grixis identity fits the ask, supplying the removal, cantrips, and finishers worth casting on the house.