4 Oct 2004
You have to sacrifice a Swamp for each black mana in the activation cost. If you use Pestilence with {B}{B}{B}{B}, that’s 4 activations with {B} each so you sacrifice 4 Swamps.
1 Aug 2008
A hybrid symbol that is both black and another type is a black mana symbol, regardless of what cost is paid for it.
8 Jun 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.