Opalescence

The card that taught a generation of players to read enchantment text twice. The whole engine lives in one global static: every other non-Aura enchantment becomes a creature whose base stats scale off its mana value, so cheap enchantments become trivial bodies and expensive ones become real threats. That single line retroactively grants enchantments a stat line the color pie never intended them to have, and it anchored an entire deckbuilding category, the enchantment-creature shell, long before bestow or constellation formalized the idea. It remains the reference point for any card that blurs the line between permanent and threat. The interaction that made it famous pairs it with Parallax Wave: animate the Wave, exploit its fading counters, and the resulting loop exiles an opposing board permanently, a one-sided lock rather than a kill, since nothing here deals damage on its own. There is a built-in cost to running it, though, and it is the same property that makes it sing: the effect is mandatory and global, so every other non-Aura enchantment picks up a body whether you want one or not, suddenly dying to creature removal it never feared. Note the asymmetry the text bakes in: it animates each other enchantment, never itself, so it stays an enchantment-only static while everything around it walks. The skill is not in choosing what to animate (you cannot) but in building a board that survives being animated all at once.