Bring the Ending

Mana Leak with an escalation clause bolted on: pay two or lose the spell, unless your opponent has already been ground down to three poison, at which point the tax evaporates and it becomes a hard counter for the same investment. That conditional is the whole design lever. A soft counter's weakness is well understood: as the game goes long and mana untaps, the two-mana tax becomes trivial to pay, and the card rots in hand. This one solves that decay problem by tying its reliability not to your own resources but to the damage your board has already done. In a deck built to accrue poison, the tax window is a stopgap for the opening turns and the hard counter is the payoff once the plan comes online, so the card sharpens exactly as the opponent's position deteriorates. The corrupted threshold is the friction that makes the free upgrade fair: three poison is not a number a control shell stumbles into by accident, so the hard-counter mode is real reward for committing to a proactive infect-adjacent gameplan rather than a splash. It reframes what has usually been a color-pie tension: blue's permission wants to sit back, but this asks the pilot to be pressing an aggressive clock, and it counters best precisely when a pure control deck would least need the help.