Acid Rain

Four mana to delete every Forest on the battlefield, no triggers, no upkeep cost, no clever clause: this is the blue entry in the old color-hoser cycle, the one-shot sorceries built to punish a single enemy's manabase. The lineage runs through Flashfires, Tsunami, and Boil, each pointing the gun at one basic land type and firing once. Acid Rain is the odd member because blue is not supposed to interact with lands by destroying them; it sits in the small archive of "blue does what blue normally cannot, but only against one enemy" effects that the color pie has since walked away from. The four-mana cost is the only restraint built into it, and against a green deck leaning on Forests it was frequently game over on resolution: a rate that read as reasonable in 1994 and absurd by any modern standard. Cards like this are why the design philosophy quietly retired the pure color hoser. A blank-on-resolution answer that ends games on cast is a feel-bad slot for both players, and a too-cheap one is a metagame distortion. Acid Rain survives mostly as a historical document of how bluntly early design was willing to dismantle one color's mana base, and of a time when the asymmetry of that punishment was considered a feature rather than a problem to be designed out.