Sporocyst

The clever part is that the same X pays twice. Ravenous scales the body, Spore Chimney scales the ramp, and both key off the identical number you sank into casting it, so a card with a mana value of 1 becomes an arbitrarily large investment sink that converts mana into a defensive wall and a fistful of tapped lands in a single action. Defender caps the ambition honestly: no matter how many counters land on it, this is a blocker, not a beater, one that leaves you with more mana available next turn than you had this turn. That reframes the whole card as a green ramp spell wearing a 0/0 body, functioning more like a mass-fetch effect than a creature you cast to attack with. The draw-a-card rider at X of five or more is the incentive to commit hard rather than trickle it out at small values, rewarding the player willing to dump a whole turn into it. It is tidy design in that everything on the card points the same direction: pay more, get more, and never mistake the result for offense.