Zoanthrope

A single X pays for three things at once here, and that triple-scaling is what separates the card from most X-spell creatures. The Ravenous X sets the body, the Warp Blast X aims a burn spell anywhere on entry, and crossing the five-counter threshold folds in a card, so every additional point of X buys stats, reach, and removal in one purchase. That efficiency is why the ceiling matters: at low X you get a flier holding up ward, at high X you get a game-ending creature that also clears a blocker or points lethal at a face on the way in. Because the Warp Blast trigger hits any target, it doubles as a way to kill the thing that would otherwise stop the attack, or as the last few points of a burn plan the moment the creature resolves. Ward is the tax that protects the investment: having sunk a large X into the body, you are not handing it away to the first cheap removal spell, which keeps the mana you committed from evaporating on the next turn. The Tyranid flavor of a creature that scales with what it consumes runs right through the split-value structure (body plus direct damage plus a conditional draw, all keyed off the same variable), and it is a cleaner expression of "spend more, get more across multiple axes" than most creatures that try to be a spell and a threat at the same time.