Corpse-Brew Bog

Corpse-Brew Bog enters the battlefield tapped.
{t}: Add {b}.
Whenever a creature dies, if you control a Swamp
and don't control a Plains, Island, Mountain, Or
Forest, you may pay {3}{b}. If you do, target
player sacrifices a creature. Activate this ability
only if Corpse-Brew Bog is untapped.