Kor Haven

The activated ability that prevents all combat damage from one attacker is the design that turned a utility land into a soft Maze of Ith you could also count as a mana source. Where Maze of Ith asks for no mana and produces none, this card splits the difference: it taps for colorless on turns you do not need the fog, then becomes a repeatable single-attacker shield when one big threat is doing the work. The prevention has to be set up before damage, so the defender activates it in the declare blockers step, after blocks are locked in, to read the board and blank the opponent's biggest swing without committing a creature or a card. The legend rule and the white pip in the activation are the discipline that keep the rate honest: you run one, and you only get the shield in a deck already leaning on white for its mana. That made it a manabase slot that doubled as a defensive answer, prized by control and prison strategies trying to neutralize a single oversized beater turn after turn. The targeting is exactly why it is a poor answer to a wide board: it only ever stops one creature, so a swarm of small attackers walks right past it. It does nothing on offense and nothing against noncombat damage; the entire pitch is that a land, by itself, can absorb the best attacker your opponent has, each turn you spare the white and the tap.