Jace's Phantasm

For one blue mana, this is a 1/1 flier that idles until a number on the other side of the table moves: the proposition is whether an opponent's graveyard ever crosses ten cards, and once it does, the body becomes a 5/5 evasive clock that cost a single mana. The condition is binary and outward-facing: it counts only an opponent's graveyard, not your own, so the threshold gets met by you putting their cards into the bin (a milling subtheme alongside the beatdown) rather than by self-mill or anything you fuel from your side. The moment the tenth card lands, the body snaps to full size with no ramp-up, and it shrinks the instant the count dips back below ten. That volatility is the price of the rate: catch it on your turn and you face a 5/5, but a single graveyard-exile effect dragging the opponent under the threshold reverts it to a 1/1 that trades down against almost anything in combat. The design lesson is in how cheaply blue buys a real threat by outsourcing the size to the opponent's own board state rather than to mana or card investment, turning a deck's disruptive plan into a switch that arms a beater. It is the rare aggressive blue creature whose growth you advance by attacking the opponent's library, not their face.