Emerald Nightmare

{t} Add {b} to your mana pool.
{1}{b},{t}: Put a -1/-1 counter on target creature.
If that creature dies this turn, create a 1/1 black
Satyr creature token.
{3}{b}{b},{t}, Sacrifice a creature: Target creature
gets -X/-X until end of turn, where X is the sacrificed creature's toughness. Activate this
ability only if you control a black creature with converted mana cost 5 or greater.