Plague Myr

Infect mana creatures are a tiny club, and the design tension behind them is real: a creature that taps for mana wants to sit back and survive, while an infect creature wants to commit to the red zone, because ten poison closes a game faster than twenty life ever does. This little Phyrexian resolves that conflict by being both at once. The body is fragile and the clock it offers is slow, but the colorless tap ability gives it reach: it powers out artifacts and infect creatures regardless of the deck's colors, then, once the board stalls, the same 1/1 can wander into combat as a last point of poison nobody bothers to block. It also fits the broader corruption shell as a creature whose every point of combat damage feeds proliferate and -1/-1 counter strategies rather than ordinary life loss, so the ramp and the kill condition draw from the same well. A generic mana dork accelerates your plan; this one accelerates the plan and can quietly become the plan, that asymmetry doing the real work. It asks nothing of you in exchange (no life, no poison on your own side, just the mana) and trades immediate power for a patient, grinding inevitability that an infect deck is happy to wait on.