Haunted Guardian

First strike on a defender is a contradiction the rules barely let you see: a creature with defender cannot attack, so its combat keyword only ever fires on defense, when something runs into it. Pair the two and the 2/1 body becomes a colorless gatekeeper that strikes first against any ground attacker, killing whatever it can finish off in the first-strike step before taking damage back. With two power, it deals lethal to anything with two or fewer toughness on the swing in; with one toughness of its own, it survives only when that first-strike damage clears the attacker entirely. The math is deliberately narrow. A 1/3 walks past it cleanly, absorbing the two damage and answering with one to drop the guardian; a 3/3 walks through worse: the guardian's two damage in the first-strike step does nothing to a three-toughness body, and then it dies to the return three with nothing to show for it. Inside the band where its two power is lethal, though, this absorbs and punishes early aggression rather than merely chump-blocking, which is more than a vanilla wall would manage. As a colorless artifact it asks nothing of a manabase, which is the whole reason a blocker this modest exists: a clean speed bump while the real plan assembles. The appeal is structural. Defender plus first strike reads like two keywords cancelling out, but they resolve into a single coherent job: taxing attackers for connecting at all.