Ice Cave

A counterspell that asks everyone to pay for it, which is a strange thing for an enchantment to sit there and do. The design idea is offering each opponent (and, in multiplayer, every other player) a chance to counter any spell by matching its exact mana cost, color pips included. That clause turns the act of countering into an auction of resources: nobody gets a free Counterspell, they get the option to pay full retail to deny a spell, and whether it is worth doing depends entirely on what is being cast and how much mana is sitting open. It belongs to the small family of Apocalypse cards built to break the two-color mold and reward open mana in a deck that can leave it up, but its real life is as a political instrument. In a single duel it is mostly a tax that punishes tapping out, since the controller can hold mana to counter their opponent's spells in return. Spread across a table, it becomes a shared veto: any player can spend to stop a spell, which makes it a tool for slowing down the table's biggest threats without the Ice Cave's controller having to lift a finger. The symmetry that makes it unreliable one-on-one is exactly what makes it interesting when there are more hands on the resources.