Thunderclap

Late in a game where your draws have stopped mattering, a redundant land becomes three damage at the perfect window. That is the trade on offer: feed a Mountain to the spell instead of spending mana, and you get instant-speed creature removal that stays live after the rest of your hand has gone inert. The Mountain doesn't even need to be untapped, so you can tap it for something useful first and then sacrifice the already-spent land to Thunderclap in the same turn, wringing two jobs out of one permanent. It also lets you keep an answer up without holding red mana you might want for a burn spell elsewhere. The catch sits in the math: every land you pitch shrinks the board you're still playing on, so you have to weigh whether the creature in front of you justifies stepping back down your curve. This is the pitch-a-Mountain mechanic pointed at creatures rather than at the wider reach of Fireblast, an early-era way to make a narrow effect playable without bending a deck's mana around it. Three damage to a single target was never going to anchor a removal suite on rate alone; what gives the card a second life is that the option to pay in lands keeps it relevant precisely when flooding would otherwise turn a dead draw into a wasted turn.