Vector Asp

Most infect creatures wrote the keyword in as a static line: the poison was always on, and the body's combat profile never changed. Here the design splits infect off and prices it as a black activation, so the creature deals ordinary combat damage until you pay the mana, at which point poison switches on for a single combat step. That gives the card two distinct combat profiles depending on whether the mana is available, which matters more than the body suggests. An unpaid attacker trades into removal and blocks like chaff; a paid one converts even one point of unblocked damage to a player into a permanent poison counter, and any combat damage it deals to a blocking creature lands as a -1/-1 counter rather than wash-away damage. Because the activation can wait until after blockers are declared, an opponent has to respect the poison line whenever black mana is open, while you keep the option to bluff it and spend the mana elsewhere. The arithmetic is the brutal math infect always ran (ten poison and a player is dead), but the on-demand framing turns a one-drop into a recurring threat that scales with how long it survives rather than a one-shot beater. It is the cheapest possible commitment to a poison clock: the creature you play early knowing the counters it stacks later will never be wiped off the board the way regular combat damage is.