Contamination

{2}{B} · Enchantment

At the beginning of your upkeep, sacrifice this enchantment unless you sacrifice a creature. If a land is tapped for mana, it produces {B} instead of any other type and amount.

Motor: se resuelve a mano

Rulings (3)

External effects that generate more mana still generate their additional mana as directed without being affected by this card. Effects which generate more mana based on what type of mana the land produces will be affected in color but not in amount.
Wizards of the Coast · 2004-10-04
The second ability of this card is a replacement effect, not a triggered ability.
Wizards of the Coast · 2004-10-04
You choose whether to sacrifice a creature or not on resolution. If not, then you sacrifice Contamination. You can choose to not sacrifice even if you no longer control Contamination on resolution.
Wizards of the Coast · 2004-10-04