Savra, Queen of the Golgari

Oracle Text

Whenever you sacrifice a black creature, you may pay 2 life. If you do, each other player sacrifices a creature.

Whenever you sacrifice a green creature, you may gain 2 life.

Card Rulings

10/1/2005 These abilities trigger specifically when you “sacrifice” a creature. They won’t trigger when a creature is put into your graveyard for any other reason.
10/1/2005 Savra itself doesn’t let you sacrifice creatures, and you can’t sacrifice them spontaneously. You must have another spell or ability that lets you sacrifice creatures.
10/1/2005 Sacrificing a creature that’s both black and green will make both abilities trigger. You may put them on the stack in whichever order you want.