Dinosaur Egg

Growing counters and a death payoff sit on the same 0/3, which is more design tension than it first looks. Evolve wants this thing to survive: every bigger creature you land stacks another counter, and each counter it accumulates raises the toughness that feeds the death trigger. The card is built to grow, then die, and cash out for exactly as much as it grew. Discover X reading off toughness is the wrinkle that ties the two halves together. A freshly cast Egg dies for a discover 3, hitting a spell of mana value 3 or less; nurse it up with a few evolve triggers and that number climbs alongside the body, so the same card converts into a bigger free spell the longer it lives. That is an unusual shape for a two-drop: most cheap green bodies want to be big or want to trade, while this one wants to be traded once it has fattened up. It reverses the usual instinct to protect a growing creature; here the counters are just a bet on how large the eventual free spell should be, and the natural exit is to let combat or a sacrifice outlet collect. That makes it a card that rewards a board still deploying threats (to feed evolve) alongside a deck that can afford to spend the Egg on purpose (to trigger discover), a narrower ask than a vanilla wall but a more interesting one.