Reverberation

A counterspell that doesn't counter. Reverberation engages the stack sideways: rather than removing a sorcery, it redirects the damage that sorcery would deal back at its caster, turning a Disintegrate or a Fireball into a self-inflicted wound. The design comes from a window when Wizards was still mapping out what blue's relationship to the stack should look like, before Counterspell ossified into the default and reactive blue cards started looking uniform. The narrowness is severe: sorcery only, damage only, and at four mana the rate is brutal against the burn spells of its era. But the structural idea is sharp, and it carries a flavor of judo that pure countermagic doesn't: the opponent pays the mana, picks the target, puts the spell on the stack, and then eats it. Later cards have revisited the redirect-damage-to-controller pattern in narrower or broader forms (Deflecting Palm is the modern cousin, though it works off combat and noncreature spells rather than the sorcery restriction), but Reverberation is the early proof of concept, printed when the rules around damage redirection were still being worked out on the fly. It rewards study for how it thinks more than for anything it does at the table.