Shifting Wall

A blocker priced entirely by how much you can pay for it, with no body until the X resolves. The design trick here is parking all the variability in the counters rather than the printed stats: the card itself is a 0/0 that would die immediately if it entered with nothing, so the X is not optional padding but the whole creature. That makes it a flexible defensive sink for an X-spell shell, scalable in the early game when you can only afford a small wall and respectable late when surplus mana would otherwise sit idle. Defender keeps it honest; the card is a wall in the literal sense, a way to convert leftover mana into toughness without ever threatening to turn the corner. Because the counters are permanent +1/+1 markers rather than a one-time toughness pump, anything that doubles counters or moves them off the wall finds real value, and any sweeper that ignores toughness collapses it like any other body. It belongs to the small family of artifact creatures whose mana cost is their stat line, a clean piece of engineering that asks one question (how much do you have to spend?) and answers it the same way every time.