Curse of the Tomb

When Curse of the Tomb enters the battlefield, put a plague counter on each creature you don't control.
All plagued creatures get -1/-1 and have: "Whenever this creature taps, add {b} to your mana pool, then you lose life equal to the number of {b} in your mana pool."
Greedy trespassers in the lost tombs of the Old Gods quickly discover why they remain lost.