Vial of Poison

One mana down, one mana to activate, and a sacrificed artifact buys a single creature's worth of deathtouch for one turn: a rate that explains why this kind of effect has always lived at the bottom of the rarity stack. Deathtouch tricks live or die on the threat of the trade. A 1/1 that suddenly kills anything it blocks rewrites the opponent's combat math; an attacker that can no longer be safely double-blocked forces bad chumps. The trouble is the premium. You are burning a card and two total mana to do for one turn what a creature with the keyword does for free and forever, and the whole effect is dead unless combat actually happens. What the card does have is timing. The activation is instant-speed, so the sacrifice waits until blocks are declared, letting you point the deathtouch at whichever threat the opponent commits to. But that flexibility is narrow, and the math is honest about its limits: using the Vial to make a blocker trade with an attacker spends two of your cards (the artifact and the blocker) to remove one of theirs, a card-disadvantageous exchange you only accept when the attacker is worth far more than the bodies it eats. The artifact also sits face-up the whole time, so the opponent attacks knowing the threat exists. This is colorless combat insurance for a shell that wanted to threaten an even trade without running removal proper, and it fills that slot and little else.