Grow Extra Arms

Green pump spells live and die by the discount, and this one prices its best turn behind a creature type. Cast on anything, it is a plain +4/+4 for two mana at instant speed: a fine combat trick, nothing that reshapes a game. Cast on a Spider, it drops to a single green mana, and that is where the card starts talking about the deck it wants to be in. The cost reduction is the whole balancing lever: two mana for a generic +4/+4 is a rate green has printed many times over, so the design bolts a tribal condition to the front rather than the back, rewarding the build that has already committed to a wall of reach blockers. It is a template Wizards has leaned on for years, where a spell reads at a workmanlike rate for the table and a premium rate for the one deck that meets its requirement. The flavor lands cleanly too: the extra arms are the Spider's, and the discount is the payoff for having eight legs to begin with. What it is not is a trick you build around in a vacuum; the pump is generous but the ceiling is fixed, so the interesting version of this card only shows up when a Spider is already on the battlefield waiting to be made enormous at the cost of one mana.