Armor of Thorns

Two mana for +2/+2 is unremarkable enchantment math; the printed bonus is the floor, not the hook. What the card actually sells is timing freedom with a built-in toll. You can drop the aura in during an opponent's attack or before blocks to spring a surprise on a creature, then settle up: cast it outside a sorcery window and the aura is sacrificed before your next turn opens, so the creature keeps its body while the +2/+2 lasts only that turn. The trick is a one-turn loan, and what you forfeit is the enchantment, not the creature wearing it. That tether is the discipline that makes the option safe to print: the upside (instant-speed combat math) and the downside (the buff evaporates the same turn) ride on the same decision, and you square the debt before the turn rolls over. Mirage was working out how to price a permanent's timing freedom against a self-destruct clause, the same balancing logic that later surfaced across permanents granting flash-like access in exchange for a delayed exile or sacrifice. The targeting restriction matters too: the aura can only land on a nonblack creature, a color-pie line that keeps green's combat tricks from propping up the colors green is supposed to lose to.