Drought

Oracle Text

At the beginning of your upkeep, sacrifice Drought unless you pay WW.

Spells cost an additional "Sacrifice a Swamp" to cast for each black mana symbol in their mana costs.

Activated abilities cost an additional "Sacrifice a Swamp" to activate for each black mana symbol in their activation costs.

Card Rulings

10/4/2004 You have to sacrifice a Swamp for each black mana in the activation cost. If you use Pestilence with , that’s 4 activations with each so you sacrifice 4 Swamps.
8/1/2008 A hybrid symbol that is both black and another type is a black mana symbol, regardless of what cost is paid for it.
6/8/2016 Activated abilities contain a colon. They’re generally written “[Cost]: [Effect].” Some keywords are activated abilities and will have colons in their reminder text.