Wall of Resurgence

The defensive shell is the disguise. A 0/6 with Defender parks itself in front of the ground game and reads as inert, but the enters trigger reaches into your manabase and stakes one of your lands as an attacker with haste that still taps for mana. The animation is the wrinkle: land-animation usually comes from a recurring source (the creature-lands, the activated-ability lands) you can re-fire after a wipe, accepting that an animated land eats removal other lands never face. This bundles the wall and a one-shot animation into one card, so you keep a permanent blocker and, on the turn it resolves, an attacker the opponent was not counting as a threat. The tension it resolves is that a wall is dead on offense and a bare land-animator is dead on defense; stapling the two produces a body that holds the line all game while opening a surprise swing immediately. The cost lives in the counters. They are not extra mana, since the land already tapped for its color; they are raw stats grafted onto a permanent that now dies like a creature. Answer the animated land and you lose both the land and its counters at once: counters cease to exist when their permanent leaves, so any removal aimed at the attacker also strips a mana source. You are wagering part of your board on a body the opponent can punish two ways with a single card.