Gush

The free spell that taught a generation of blue mages what land really costs. Printed with a five-mana sticker price nobody ever pays, its actual cost is two Islands bounced to hand: a tempo hit you recoup by replaying lands you would draw anyway. That arithmetic is the whole card. In a deck built to refund the bounce (cantrips, cheap lands, ways to turn the floating mana into pressure), Gush is functionally a zero-cost draw-two that also thins the board and resets fetchable triggers. The genius and the danger both live in the alternative cost: it scales with how thoroughly you have abused the rest of your spells, so the more degenerate the shell, the closer to free it gets.

That made it a recurring restricted-list resident in formats where a free, repeatable card-advantage engine plus a graveyard or storm payoff was too much to leave open; Wizards has toggled it on and off the Vintage restricted list more than once, treating it less as a card than as a knob for how fast blue is allowed to draw. Strip away the era-specific combo decks it has anchored and the underlying design lesson holds: a spell with a non-mana alternative cost is only ever as fair as the cheapest way to satisfy it, and Gush asks for the one resource every deck already has in surplus.