Corridor Monitor

The untap trigger on a two-mana body looks like combat filler and functions like a combo enabler. Read it as a defensive body and it is a 1/4 that gums up the ground with a minor bonus; read it as a repeatable untap effect stapled to a creature you can flicker or reanimate, and it becomes an engine piece. Untapping a mana rock recovers the mana spent casting it, which is the seed of countless artifact-mana loops; untapping a creature refreshes a tap ability, whether that is a mana dork, a pinger, or something more baroque. The card cares nothing about what it untaps or why, and that indifference is the whole danger in the hands of someone who does. The body deserves note too: 1/4 is a genuinely awkward stat line to attack into, so the construct earns its keep on defense while the value players build toward whatever the untap actually breaks. This is the recurring problem with cheap creatures that carry a fully generic, no-strings enters trigger: designers can price the body honestly, but they cannot price every future card the trigger will be pointed at. A construct that untaps target artifact or creature you control is a blank check written to a combo player, and the interesting part is always the payoff, not the check.