Infernal Darkness

Oracle Text

Cumulative upkeep—Pay B and 1 life. (At the beginning of your upkeep, put an age counter on this permanent, then sacrifice it unless you pay its upkeep cost for each age counter on it.)

If a land is tapped for mana, it produces B instead of any other type.

Card Rulings

10/1/2008 This effect changes the type of mana produced, but not the amount. For example, if a land that’s tapped for mana would add to its controller’s mana pool, it adds to that player’s mana pool instead.