Like most Magic: The Gathering cards, the value of Mana Leak depends on a few consistent factors: its rarity, the printing and finish (regular or foil), its physical condition, and the set it was printed in (Magic Player Rewards 2005)
Like many right before Dimir strikes, I was stunned senseless
There are indeed 10 2000-counters, but for the most part, the hope is to draw them as triggers after losing a life point
Accounting for poison damage at the end of the turn, Muk can effectively one-shot Mewtwo EX
If Im not giving enough credit to a particular white instant, let me know
So we have some removal and then a good defense against attack