Brine Elemental

Skipping an opponent's untap step is one of the rare effects that buys you a turn without ending the game outright, and the morph wrapper is what turns a clunky payoff into a combo engine. The trigger fires on turning face up, not on entering or attacking: cast face down for three, then pay the morph cost to flip so the opponent's tapped permanents stay tapped through their next untap step. Repeat that flip on a loop and they never untap at all. That timing window is exactly the hook that pairs the card with effects re-morphing creatures at instant speed. The notorious build looped it with Vesuvan Shapeshifter, which can copy Brine Elemental and re-flip itself each upkeep, generating a perpetual untap-lock that simply denied the opponent any meaningful turn. The two-card engine became a defining soft-lock of its constructed era, the kind of prison that wins not by burning life totals but by cutting off access to mana and blockers indefinitely. On its own, the 5/4 body is a serviceable beater with a tempo swing stapled to its flip, rarely a card you regret drawing. The design tension lives in the gap between those two readings: a fair midrange creature in isolation, a hard lock the moment a second piece lets you flip it at will. Morph hides which one you are holding until the mana is already committed.