Fog Bank

The defensive blocker stripped to its cleanest possible expression: a wall that absorbs any attacker and walks away unscathed, no matter the size. The damage-prevention clause is the whole design. A 0/2 body would chump-block once and die; this one stops a 10/10 turn after turn, because the combat damage simply never happens in either direction. Flying on a Defender looks like a contradiction (it cannot attack), but it lets the wall sit in front of evasive threats that an ordinary ground blocker would let through, which is the detail that separates this from a generic Wall. The cost of that immortality is paid up front: it generates nothing, threatens nothing, and asks the deck around it to convert bought time into a win. That trade is exactly why it became the perennial blocker for slower blue decks that want to stall the board and let a slower plan mature. Where a removal spell answers one creature, this answers one attacker indefinitely, asking only that the attacker keep choosing to swing into it. The whole package reads as a thesis on what a defensive permanent is for: not to trade, not to threaten, but to make one lane of the battlefield permanently safe and let the clock run out on the opponent's tempo.