Instill Infection⁣ - Scars of Mirrodin⁣ (Common)⁣ [68]

Instill Infection allows you to place a -1/-1 counter on any target creature, weakening it significantly, and also lets you draw a card. This instant is valuable in decks that focus on counter synergies or creature removal, providing both disruption and card advantage. However, the mana cost can be a bit steep for quick plays, so it's best suited for mid to late-game strategies.