Opal Champion

Sitting on the battlefield as nothing but an enchantment, this is a trap baited with the one thing an opponent cannot avoid doing: casting a creature. The moment they commit a creature spell to the stack, the enchantment flips into a 3/3 first striker, and the new body is on the board before their freshly cast creature has even resolved. That timing is the whole design. The transformation triggers off the cast, not the resolution, so the threat materializes during a window the opponent opened themselves, and a 3/3 with first strike dominates the combat math against most of the bodies it would punish. The enchantment shell does double duty: it dodges sorcery-speed creature removal while dormant (an opponent holding a kill spell has nothing to point it at), and it sidesteps the sweepers and burn that would answer a creature on an empty board. The cost is inertness. Against a controlling deck that never casts a creature, it remains a enchantment that sits idle forever, a bet that the opponent's plan involves creatures. The design comes from an Urza's-block strain of permanents that lie in wait as enchantments and animate in response to specific triggers, an idea that traded reliability for the ability to punish an opponent's own line of play.